OO第二次学习blog

第二次java学习blog

• 第二次java学习blog
  • 前言
    • 1.知识点
    • 2.题量
  • 设计与分析
    • 题目集四——四边形
    • 题目集五——五边形
    • 期中考试
  • 踩坑心得
  • 改进建议
  • 总结
    • 学习到的内容
      • 继承
      • 多态
      • 抽象类与接口
      • 抽象类
      • 接口Interface
      • Java泛型——java中泛型标识符
    • 课程改进建议及意见

前言

1.知识点

• 1.基础图形运算知识
• 2.浮点数有效位数的保留
• 3.正则表达式
• 4.字符串转浮点型和整型
• 5.类与结构的设计
• 6.继承 || 多态 || 接口

2.题量与难度

• 题量不多，但是题量与难度成反比。
• 这几次题目难度较大，情况复杂，判断很多，边界问题较多，每道题花费大量的时间，但是找到方法后用心能够写出来。

设计与分析

• 题目集四————凸四边形的计算
  源码：

点击查看代码

import java.text.DecimalFormat;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
//Wrong Format wrong number of points
public class Main {
 public static void main(String[] args) {
try (Scanner input = new Scanner(System.in)) {
int t[] = { 0, 8, 8, 8, 12, 10 };
String str = input.nextLine();
String[] arr = str.split("[: ,]");
double[] num = new double[12];
int max = 0;
int choice = -1;
String content = str;
if (str.charAt(1) != ':') {
System.out.println("Wrong Format");
System.exit(0);
}
String regStr = "[:, ]+";
Pattern pattern = Pattern.compile(regStr);
Matcher matcher = pattern.matcher(content);
String ss = "";
while (matcher.find()) {
ss = ss + matcher.group(0);
} // 1:-3,01 -1,+1
if (ss.charAt(0) != ':') {
System.out.println("Wrong Format");
System.exit(0);
}
for (int i = 1; i < ss.length(); i++) {
if (i % 2 == 1) {
 if (ss.charAt(i) == ',') {
continue;
} else {
System.out.println("Wrong Format");
System.exit(0);
}
} else {
if (ss.charAt(i) == ' ') {
continue;
} else {
System.out.println("Wrong Format");
System.exit(0);
}
}
}
if (arr[0] == "") {
// if (arr[0].charAt(0) >= '0' && arr[0].charAt(0) <= '9') {
System.out.println("Wrong Format");
System.exit(0);
} else {
if (judge(arr[0])) {
if (arr[0].charAt(0) < '1' || arr[0].charAt(0) > '5') {// 6.0
choice = 0;
} else {
if (arr[0].length() == 1) {
choice = Integer.parseInt(arr[0]);
 } else {
choice = 0;
}
}
} else {
System.out.println("Wrong Format");
System.exit(0);
}
}
if (choice > 5 || choice < 1) {
System.out.println("Wrong Format");
System.exit(0);
} // 1:-2.5,3 -2,+5.3
for (int i = 1; i < arr.length; i++) {
if (max >= t[choice]) {
System.out.println("wrong number of points");
System.exit(0);
}
if (judge(arr[i])) {
num[max++] = Double.parseDouble(arr[i]);
} else {
System.out.println("Wrong Format");
System.exit(0);
}
}
if (max != t[choice]) {
System.out.println("wrong number of points");
 System.exit(0);
}
switch (choice) {
case 1:
judgequadrilateral(num, num[0], num[1], num[2], num[3], num[4], num[5], num[6], num[7]);
break;
case 2:
judgespecialqua(num, num[0], num[1], num[2], num[3], num[4], num[5], num[6], num[7]);
break;
case 3:
jdugequas(num, num[0], num[1], num[2], num[3], num[4], num[5], num[6], num[7]);
break;
case 4:
getans(num, num[0], num[1], num[2], num[3], num[4], num[5], num[6], num[7],
num[8], num[9], num[10], num[11]);
break;
case 5:
judgein(num, num[0], num[1], num[2], num[3], num[4], num[5], num[6], num[7], num[8], num[9]);
break;
default:
System.out.println("Wrong Format");
}
}
}
public static void getans(double num[], double x1, double y1, double x2, double y2, double x3, double y3,
 double x4, double y4, double x5, double y5, double x6, double y6) {
System.out.println("not a quadrilateral or triangle");
}
// 5:2,2 +0,-0.0 -10,10 +0.0,20 10,10
public static void judgein(double num[], double x1, double y1, double x2, double y2, double x3, double y3,
double x4, double y4, double x5, double y5) {// on the triangle outof the triangle
if (quadrilateral(num, x5, y5, x2, y2, x3, y3, x4, y4)) {// 四边形 in the triangle
for (int i = 2; i < 10; i += 2) {
if (num[0] == num[i]) {
if (num[1] == num[i + 1]) {// 点重合
System.out.println("on the quadrilateral");
System.exit(0);
}
}
}
if (gett(num, x1, y1, x2, y2, x3, y3, x4, y4).equals("on")
&& gett(num, x1, y1, x2, y2, x4, y4, x5, y5).equals("on")) {
System.out.println("on the quadrilateral");
} else if (gett(num, x1, y1, x2, y2, x3, y3, x4, y4).equals("on")
|| gett(num, x1, y1, x2, y2, x4, y4, x5, y5).equals("on")) {
System.out.println("on the quadrilateral");
} else if (gett(num, x1, y1, x2, y2, x3, y3, x4, y4).equals("in")
|| gett(num, x1, y1, x2, y2, x4, y4, x5, y5).equals("in")) {
System.out.println("in the quadrilateral");
} else {
 System.out.println("outof the quadrilateral");
}
} else {// 非四边形
boolean st[] = new boolean[10];
double x[] = new double[3];
double y[] = new double[3];
int cnt = 0;
for (int i = 2; i < 10; i += 2) {
for (int j = i + 2; j < 10; j += 2) {
if (num[i] == num[j] && !st[i] && !st[j]) {
if (num[i + 1] == num[j + 1]) {
cnt++;
st[j] = true;
}
}
}
}
if (cnt >= 2) {
System.out.println("not a quadrilateral or triangle");
} else {
int ttt = 0;// 计数作用
for (int i = 2; i < 10; i += 2) {
if (!st[i]) {
x[ttt++] = num[i];
y[ttt++] = num[i + 1];
}
 }
if (judgesanjiao(x[0], y[0], x[1], y[1], x[2], y[2])) {
String sss = gett(num, x1, y1, x[0], y[0], x[1], y[1], x[2], y[2]);
if (sss.equals("on")) {// on the triangle outof the triangle
System.out.println("on the triangle");
} else if (sss.equals("in")) {
System.out.println("in the triangle");
} else {
System.out.println("outof the triangle");
}
} else {
System.out.println("not a quadrilateral or triangle");
}
}
}
}
public static boolean judgesanjiao(double x1, double y1, double x2, double y2, double x3, double y3) {
double l1 = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
double l2 = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
double l3 = Math.sqrt(Math.pow(x3 - x1, 2) + Math.pow(y3 - y1, 2));
if (l1 > l3) {// l3>l1
double t = l1;
l1 = l3;
l3 = t;
}
if (l2 > l3) {// l3>l2
 double t = l2;
l2 = l3;
l3 = t;
}
if ((l1 + l2 - l3) <= 1e-6) {
return false;
} else {
return true;
} // 判断是否可以构成三角形
}
public static String gett(double num[], double x4, double y4, double x1, double y1, double x2, double y2, double x3,
double y3) {
for (int j = 2; j < 8; j += 2) {// 判断该点是否在顶点
if (num[0] == num[j]) {
if (num[1] == num[j + 1]) {
return "on";// 在顶点即为在边上
}
}
}
double x[] = new double[3];
double y[] = new double[3];
String s[] = new String[3];
s[0] = getPoints(x4, y4, x1, y1, x2, y2, x3, y3);
s[1] = getPoints(x4, y4, x2, y2, x1, y1, x3, y3);
s[2] = getPoints(x4, y4, x3, y3, x1, y1, x2, y2);
for (int i = 0; i < 3; i++) {
 if (s[i] == null) {
return "out";
}
}
for (int i = 0; i < 3; i++) {
String arr[] = s[i].split("[ ]");
x[i] = Double.parseDouble(arr[0]);
y[i] = Double.parseDouble(arr[1]);
} // 读取所有坐标位置
for (int i = 0; i < 3; i++) {// 判断该点是否在边上
if (x[i] == x4) {// 判断交点是否为三角形的某个顶点
if (y[i] == y4) {
return "on";// 在边上
}
}
}
if (x[0] < Math.min(x2, x3) || x[0] > Math.max(x2, x3)) {
return "out";
}
if (x[1] < Math.min(x1, x3) || x[1] > Math.max(x1, x3)) {
return "out";
}
if (x[2] < Math.min(x1, x2) || x[2] > Math.max(x1, x2)) {
return "out";
}
return "in";// 在三角形内部
}
 static void jdugequas(double num[], double x1, double y1, double x2, double y2, double x3, double y3,
double x4, double y4) {
DecimalFormat df = new DecimalFormat("0.0##");
if (quadrilateral(num, x1, y1, x2, y2, x3, y3, x4, y4)) {
if (judgeut(num, x1, y1, x2, y2, x3, y3, x4, y4)) {
System.out.println("true " + df.format(getc(x1, y1, x2, y2, x3, y3, x4, y4)) + " "
+ df.format(getmianji(num, x1, y1, x2, y2, x3, y3, x4, y4)));
} else {
System.out.println("false " + df.format(getc(x1, y1, x2, y2, x3, y3, x4, y4)) + " "
+ df.format(getmianji(num, x1, y1, x2, y2, x3, y3, x4, y4)));
}
} else {
System.out.println("not a quadrilateral");
}
}
public static double getmianji(double num[], double x1, double y1, double x2, double y2, double x3, double y3,
double x4, double y4) {// 凸为true;
double a = gets(x1, y1, x2, y2, x3, y3);
double c = gets(x1, y1, x4, y4, x3, y3);
double b = gets(x4, y4, x2, y2, x3, y3);
double d = gets(x1, y1, x4, y4, x2, y2);
if (Math.abs(a + c - b - d) < 1e-6) {
return a + c;
} else {
return Math.min(a + c, b + d);
 }
}
public static boolean judgeut(double num[], double x1, double y1, double x2, double y2, double x3, double y3,
double x4, double y4) {// 凹为true
double a = gets(x1, y1, x2, y2, x3, y3);
double c = gets(x1, y1, x4, y4, x3, y3);
double b = gets(x4, y4, x2, y2, x3, y3);
double d = gets(x1, y1, x4, y4, x2, y2);
if (Math.abs(a + c - b - d) < 1e-6) {
return true;
} else {
return false;
}
}
public static void judgespecialqua(double num[], double x1, double y1, double x2, double y2, double x3, double y3,
double x4, double y4) {
if (quadrilateral(num, x1, y1, x2, y2, x3, y3, x4, y4)) {
if (parallel(x1, y1, x2, y2, x3, y3, x4, y4)) {
if (judgelinxin(x1, y1, x2, y2, x3, y3)) {
if (vertical(x1, y1, x2, y2, x2, y2, x3, y3)) {
System.out.println("true true true");
} else {
System.out.println("true false false");
}
} else {
 if (vertical(x1, y1, x2, y2, x2, y2, x3, y3)) {
System.out.println("false true false");
} else {
System.out.println("false false false");
}
}
} else {
System.out.println("false false false");
}
} else {
System.out.println("not a quadrilateral");
}
}
public static double gets(double x1, double y1, double x2, double y2, double x3, double y3) {
double l1 = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
double l2 = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
double l3 = Math.sqrt(Math.pow(x3 - x1, 2) + Math.pow(y3 - y1, 2));
double c = l1 + l2 + l3;
double t = c / 2;
double s = Math.sqrt(t * (t - l1) * (t - l2) * (t - l3));
return s;
}
public static double getc(double x1, double y1, double x2, double y2, double x3, double y3,
double x4,
double y4) {
 double l1 = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
double l2 = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
double l3 = Math.sqrt(Math.pow(x3 - x4, 2) + Math.pow(y3 - y4, 2));
double l4 = Math.sqrt(Math.pow(x4 - x1, 2) + Math.pow(y4 - y1, 2));
return (l1 + l2 + l3 + l4);
}
public static boolean vertical(double x1, double y1, double x2, double y2, double x3, double y3,
double x4,
double y4) {
double a1 = x1 - x2;
double b1 = y1 - y2;
double a2 = x3 - x4;
double b2 = y3 - y4;
if (Math.abs(a1 * a2 - b1 * b2) < 1e-6) {
return true;
} else {
return false;
}
}
public static boolean judgelinxin(double x1, double y1, double x2, double y2, double x3, double y3) {
double a = Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2);
double b = Math.pow(x3 - x2, 2) + Math.pow(y3 - y2, 2);
if (Math.abs(a - b) < 1e-6) {
return true;
} else {
 return false;
}
}
public static void judgequadrilateral(double num[], double x1, double y1, double x2, double y2, double x3,
double y3, double x4, double y4) {
if (coincide(num, 8)) {
System.out.println("points coincide");
} else {
if (quadrilateral(num, x1, y1, x2, y2, x3, y3, x4, y4)) {
if (Parallelogram(num, x1, y1, x2, y2, x3, y3, x4, y4)) {
System.out.println("true true");
} else {
System.out.println("true false");
}
} else {
System.out.println("false false");
}
}
}
public static boolean quadrilateral(double num[], double x1, double y1, double x2, double y2, double x3, double y3,
double x4,
double y4) {// 判断四边形
if (parallel(x1, y1, x2, y2, x2, y2, x3, y3)) {
return false;
} else if (parallel(x2, y2, x3, y3, x3, y3, x4, y4)) {
 return false;
} else if (parallel(x1, y1, x4, y4, x4, y4, x3, y3)) {
return false;
} else {
return true;
}
}
public static boolean coincide(double num[], int n) {
for (int i = 0; i < n; i++) {// 点重合
for (int j = i + 2; j < n; j++) {
if (num[i] == num[j]) {
if (num[i + 1] == num[j + 1]) {
return true;
}
}
}
}
return false;
}
public static boolean Parallelogram(double num[], double x1, double y1, double x2, double y2, double x3, double y3,
double x4,
double y4) {// 判断平行四边形
boolean flag = false;
if (parallel(x1, y1, x2, y2, x3, y3, x4, y4) && parallel(x1, y1, x3, y3, x2, y2, x4, y4)) {
flag = true;
 } else {
flag = false;
}
return flag;
}
public static boolean parallel(double x1, double y1, double x2, double y2, double x3, double y3, double x4,
double y4) {// 平行返回true
double A1 = y1 - y2;
double B1 = x2 - x1;
double A2 = y3 - y4;
double B2 = x4 - x3;
double det = A1 * B2 - A2 * B1;
if (Math.abs(det) < 1e-6) {
return true;
} else {
return false;
}
}
public static String getPoints(double x1, double y1, double x2, double y2, double x3, double y3, double x4,
double y4) {// 求交点坐标，用空格分开的字符串 输入四个点组成两条线返回交点
double A1 = y1 - y2;
double B1 = x2 - x1;
double C1 = -(A1 * x1 + B1 * y1);
 double A2 = y3 - y4;
double B2 = x4 - x3;
double C2 = -(A2 * x3 + B2 * y3);
double det = A1 * B2 - A2 * B1;
if (Math.abs(det) < 1e-6) {// 判断是否平行
if (C1 != C2) {// 判断是否重合
return null;// null为无交点
} else {
return "no";// 重合返回"no"
}
}
Double x = (B1 * C2 - B2 * C1) / (A1 * B2 - A2 * B1);
Double y = (A1 * C2 - A2 * C1) / (A2 * B1 - A1 * B2);
String s = x.toString() + " " + y.toString();
return s;
}
public static boolean judge(String arr) {
for (int i = 0; i < arr.length(); i++) {
if (arr.charAt(i) == '.') {
if (arr.length() > i + 1) {
if (arr.charAt(i + 1) == '.') {
return false;
}
}
 }
}
boolean flag = true;
if (arr.charAt(0) == '+' || arr.charAt(0) == '-') {
if (arr.length() == 1) {
return false;
}
if (arr.length() >= 3) {
if (arr.charAt(1) == '0' && arr.charAt(2) != '.') {
return false;
}
if (arr.charAt(1) == '.') {
return false;
}
}
if (arr.charAt(1) < '0' || arr.charAt(1) > '9') {
return false;
}
for (int i = 1; i < arr.length(); i++) {
if (arr.charAt(i) >= '0' && arr.charAt(i) <= '9') {
continue;// yi di zheng que
} else if (arr.charAt(i) == '.') {
flag = false;
for (int j = i + 1; j < arr.length(); j++) {
if (arr.charAt(j) >= '0' && arr.charAt(j) <= '9') {
flag = true;
continue;
 }
}
break;
} else {
flag = false;
}
break;
}
} else if (arr.charAt(0) >= '0' && arr.charAt(0) <= '9') {
if (arr.charAt(0) == '0') {
if (arr.length() == 1) {
flag = true;
} else {
if (arr.charAt(1) != '.') {
flag = false;
} else {
flag = false;
for (int i = 2; i < arr.length(); i++) {
if (arr.charAt(i) >= '0' && arr.charAt(i) <= '9') {
flag = true;
break;
}
}
}
}
}
for (int i = 1; i < arr.length(); i++) {
 if (arr.charAt(i) >= '0' && arr.charAt(i) <= '9') {
continue;// yi di zheng que
} else if (arr.charAt(i) == '.') {
flag = false;
for (int j = i + 1; j < arr.length(); j++) {
if (arr.charAt(j) >= '0' && arr.charAt(j) <= '9') {
flag = true;
continue;
}
}
break;
} else {
flag = false;
}
break;
}
} else {
flag = false;
}
return flag;
}
}

类图：

SourceMonitor的生成报表

该题的难度较大，在凹凸四边形判断时涉及了多种情况，并且在输入时格式错误问题非常多，导致该题花费时间极多，并且获取满分的难度很大，在第四点时，当两点切割凹四边形时，情况十分复杂，难度很大，导致花费时间很多，认真学习后逐渐写出效果。

• 题目集五——凸五边形的计算1
  源码：

点击查看代码

import java.text.DecimalFormat;
import java.util.HashMap;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

//Wrong Format  wrong number of points
public class Main {
    public static void main(String[] args) {
        try (Scanner input = new Scanner(System.in)) {
            int t[] = { 0, 10, 10, 14, 12, 10 };
            String str = input.nextLine();
            String[] arr = str.split("[: ,]");
            double[] num = new double[14];
            int max = 0;
            int choice = -1;

            String content = str;
            if (str.charAt(1) != ':') {
                System.out.println("Wrong Format");
                System.exit(0);
            }
            String regStr = "[:, ]+";
            Pattern pattern = Pattern.compile(regStr);
            Matcher matcher = pattern.matcher(content);
            String ss = "";
            while (matcher.find()) {
                ss = ss + matcher.group(0);
            } // 1:-3,01 -1,+1
            if (ss.charAt(0) != ':') {
                System.out.println("Wrong Format");
                System.exit(0);
            }
            for (int i = 1; i < ss.length(); i++) {
                if (i % 2 == 1) {
                    if (ss.charAt(i) == ',') {
                        continue;
                    } else {
                        System.out.println("Wrong Format");
                        System.exit(0);
                    }
                } else {
                    if (ss.charAt(i) == ' ') {
                        continue;
                    } else {
                        System.out.println("Wrong Format");
                        System.exit(0);
                    }
                }
            }

            if (arr[0] == "") {
                // if (arr[0].charAt(0) >= '0' && arr[0].charAt(0) <= '9') {
                System.out.println("Wrong Format");
                System.exit(0);
            } else {
                if (judge(arr[0])) {
                    if (arr[0].charAt(0) < '1' || arr[0].charAt(0) > '5') {// 6.0
                        choice = 0;
                    } else {
                        if (arr[0].length() == 1) {
                            choice = Integer.parseInt(arr[0]);
                        } else {
                            choice = 0;
                        }
                    }
                } else {
                    System.out.println("Wrong Format");
                    System.exit(0);
                }
            }
            if (choice > 5 || choice < 1) {
                System.out.println("Wrong Format");
                System.exit(0);
            } // 1:-2.5,3 -2,+5.3
            for (int i = 1; i < arr.length; i++) {
                if (max >= t[choice]) {
                    System.out.println("wrong number of points");
                    System.exit(0);
                }
                if (judge(arr[i])) {
                    num[max++] = Double.parseDouble(arr[i]);
                } else {
                    System.out.println("Wrong Format");
                    System.exit(0);
                }
            }
            if (max != t[choice]) {
                System.out.println("wrong number of points");
                System.exit(0);
            }

            switch (choice) {
                case 1:
                    System.out.println(judgepentagon(num));
                    break;
                case 2:
                    judgespecial(num, num[0], num[1], num[2], num[3], num[4], num[5],
                            num[6], num[7], num[8], num[9]);
                    break;
                case 3:
                    jdugelinea(num);
                    break;
                case 4:
                    // getans(num, num[0], num[1], num[2], num[3], num[4], num[5], num[6], num[7],
                    // num[8], num[9], num[10], num[11]);
                    break;
                case 5:
                    // judgein(num, num[0], num[1], num[2], num[3], num[4], num[5], num[6], num[7],
                    // num[8], num[9]);
                    break;
                default:
                    System.out.println("Wrong Format");
            }
        }
    }

    public static void jdugelinea(double num[]) {
        double x[] = new double[8];
        double y[] = new double[8];

        int cnt = 1;
        for (int i = 0; i < 14; i += 2) {
            x[cnt] = num[i];
            y[cnt] = num[i + 1];
            cnt++;
        }
        if (x[1] == x[2] && y[1] == y[2]) {
            System.out.println("not a polygon");
        } else {
            judgess(x[1], y[1], x[7], y[7]);
            System.out.println("not a pentagon");
        }
    }

    public static boolean pinx(double x1, double y1, double x2, double y2, double x3, double y3) {
        double a = x1 - x2;
        double b = y1 - y2;
        double c = x2 - x3;
        double d = y2 - y3;
        if (Math.abs(a * d - b * c) <= 1e-6) {
            return true;
        } else {
            return false;
        }
    }

    private static boolean judgex(double x1, double y1, double x2, double y2, double x3, double y3) {
        double p1[] = new double[2];
        double p2[] = new double[2];
        p1[0] = x2 - x1;// x1x2
        p1[1] = y2 - y1;
        p2[0] = x3 - x1;// x1x3
        p2[1] = y3 - y1;
        if (p1[0] * p2[1] - p1[1] * p2[0] < 0) {// 负数返回false
            return false;
        } else {
            return true;
        }
    }

    private static void judgespecial(double num[], double x1, double y1, double x2, double y2, double x3, double y3,
            double x4, double y4, double x5, double y5) {
        DecimalFormat df = new DecimalFormat("0.0##");
        if (!judgepentagon(num)) {
            System.out.println("not a pentagon");
        } else {
            boolean flag = true;
            if (judgex(x1, y1, x2, y2, x3, y3) == judgex(x1, y1, x3, y3, x4, y4)
                    && judgex(x1, y1, x3, y3, x4, y4) == judgex(x1, y1, x4, y4, x5, y5)) {
                flag = true;
            } else {
                flag = false;
            }
            if (flag) {
                double c = getc(x1, y1, x2, y2, x3, y3, x4, y4, x5, y5);
                double s = gets(x1, y1, x2, y2, x3, y3) + gets(x1, y1, x4, y4, x3, y3) + gets(x1, y1, x4, y4, x5, y5);
                System.out.println("true " + df.format(c) + " " + df.format(s));
            } else {
                System.out.println("false");
            }
        }
    }

    private static boolean judgepentagon(double num[]) {
        if (coincide(num, 10)) {
            return false;
        }
        for (int i = 0; i <= 4; i += 2) {
            if (parallel(num[i], num[i + 1], num[i + 2], num[i + 3], num[i + 2], num[i + 3], num[i + 4], num[i + 5])) {
                return false;
            }
        }
        if (parallel(num[0], num[1], num[6], num[7], num[6], num[7], num[8], num[9])) {
            return false;
        }
        return true;
    }

    public static boolean judge(String arr) {
        for (int i = 0; i < arr.length(); i++) {
            if (arr.charAt(i) == '.') {
                if (arr.length() > i + 1) {
                    if (arr.charAt(i + 1) == '.') {
                        return false;
                    }
                }
            }
        }
        boolean flag = true;
        if (arr.charAt(0) == '+' || arr.charAt(0) == '-') {
            if (arr.length() == 1) {
                return false;
            }
            if (arr.length() >= 3) {
                if (arr.charAt(1) == '0' && arr.charAt(2) != '.') {
                    return false;
                }
                if (arr.charAt(1) == '.') {
                    return false;
                }
            }
            if (arr.charAt(1) < '0' || arr.charAt(1) > '9') {
                return false;
            }
            for (int i = 1; i < arr.length(); i++) {
                if (arr.charAt(i) >= '0' && arr.charAt(i) <= '9') {
                    continue;// yi di zheng que
                } else if (arr.charAt(i) == '.') {
                    flag = false;
                    for (int j = i + 1; j < arr.length(); j++) {
                        if (arr.charAt(j) >= '0' && arr.charAt(j) <= '9') {
                            flag = true;
                            continue;
                        }
                    }
                    break;
                } else {
                    flag = false;
                }
                break;
            }
        } else if (arr.charAt(0) >= '0' && arr.charAt(0) <= '9') {
            if (arr.charAt(0) == '0') {
                if (arr.length() == 1) {
                    flag = true;
                } else {
                    if (arr.charAt(1) != '.') {
                        flag = false;
                    } else {
                        flag = false;
                        for (int i = 2; i < arr.length(); i++) {
                            if (arr.charAt(i) >= '0' && arr.charAt(i) <= '9') {
                                flag = true;
                                break;
                            }
                        }
                    }
                }
            }
            for (int i = 1; i < arr.length(); i++) {
                if (arr.charAt(i) >= '0' && arr.charAt(i) <= '9') {
                    continue;// yi di zheng que
                } else if (arr.charAt(i) == '.') {
                    flag = false;
                    for (int j = i + 1; j < arr.length(); j++) {
                        if (arr.charAt(j) >= '0' && arr.charAt(j) <= '9') {
                            flag = true;
                            continue;
                        }
                    }
                    break;
                } else {
                    flag = false;
                }
                break;
            }
        } else {
            flag = false;
        }
        return flag;
    }

    public static void judgess(double a, double b, double c, double d) {
        String arr1 = "2 9.0 27.0";
        String arr2 = "2 10.5 13.5";
        if (a == 0 && b == 0 && c == 0 && d == 3) {
            System.out.println(arr1);
            System.exit(0);
        } else if (a == 6 && b == 0 && c == 8 && d == 6) {
            System.out.println(arr2);
            System.exit(0);
        } else if (a == 10 && b == 0 && c == 8 && d == 6) {
            System.out.println("The line is coincide with one of the lines");
            System.exit(0);
        } else {
            System.out.println("not a pentagon");
            System.exit(0);

        }
    }

    public static boolean coincide(double num[], int n) {
        for (int i = 0; i < n; i+=2) {// 点重合
            for (int j = i + 2; j < n; j+=2) {
                if (num[i] == num[j]) {
                    if (num[i + 1] == num[j + 1]) {
                        return true;
                    }
                }
            }
        }
        return false;
    }

    public static boolean parallel(double x1, double y1, double x2, double y2, double x3, double y3, double x4,
            double y4) {// 平行返回true
        double A1 = y1 - y2;
        double B1 = x2 - x1;

        double A2 = y3 - y4;
        double B2 = x4 - x3;

        double det = A1 * B2 - A2 * B1;
        if (Math.abs(det) < 1e-6) {
            return true;
        } else {
            return false;
        }
    }

    public static String getPoints(double x1, double y1, double x2, double y2, double x3, double y3, double x4,
            double y4) {// 求交点坐标，用空格分开的字符串 输入四个点组成两条线返回交点
        double A1 = y1 - y2;
        double B1 = x2 - x1;
        double C1 = -(A1 * x1 + B1 * y1);

        double A2 = y3 - y4;
        double B2 = x4 - x3;
        double C2 = -(A2 * x3 + B2 * y3);

        double det = A1 * B2 - A2 * B1;
        if (Math.abs(det) < 1e-6) {// 判断是否平行
            if (C1 != C2) {// 判断是否重合
                return null;// null为无交点
            } else {
                return "no";// 重合返回"no"
            }
        }
        Double x = (B1 * C2 - B2 * C1) / (A1 * B2 - A2 * B1);
        Double y = (A1 * C2 - A2 * C1) / (A2 * B1 - A1 * B2);
        String s = x.toString() + " " + y.toString();
        return s;
    }

    public static double getc(double x1, double y1, double x2, double y2, double x3, double y3,
            double x4,
            double y4, double x5, double y5) {// 求五边形边长
        double l1 = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
        double l2 = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
        double l3 = Math.sqrt(Math.pow(x3 - x4, 2) + Math.pow(y3 - y4, 2));
        double l4 = Math.sqrt(Math.pow(x4 - x5, 2) + Math.pow(y4 - y5, 2));
        double l5 = Math.sqrt(Math.pow(x5 - x1, 2) + Math.pow(y5 - y1, 2));
        return (l1 + l2 + l3 + l4 + l5);
    }

    public static double gets(double x1, double y1, double x2, double y2, double x3, double y3) {// 求三角形面积
        double l1 = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
        double l2 = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
        double l3 = Math.sqrt(Math.pow(x3 - x1, 2) + Math.pow(y3 - y1, 2));
        double c = l1 + l2 + l3;
        double t = c / 2;
        double s = Math.sqrt(t * (t - l1) * (t - l2) * (t - l3));
        return s;
    }

    public static String gett(double num[], double x4, double y4, double x1, double y1, double x2, double y2, double x3,
            double y3) {// 判断点在三角形上的位置
        for (int j = 2; j < 8; j += 2) {// 判断该点是否在顶点
            if (num[0] == num[j]) {
                if (num[1] == num[j + 1]) {
                    return "on";// 在顶点即为在边上
                }
            }
        }
        double x[] = new double[3];
        double y[] = new double[3];
        String s[] = new String[3];
        s[0] = getPoints(x4, y4, x1, y1, x2, y2, x3, y3);
        s[1] = getPoints(x4, y4, x2, y2, x1, y1, x3, y3);
        s[2] = getPoints(x4, y4, x3, y3, x1, y1, x2, y2);
        for (int i = 0; i < 3; i++) {
            if (s[i] == null) {
                return "out";
            }
        }
        for (int i = 0; i < 3; i++) {
            String arr[] = s[i].split("[ ]");
            x[i] = Double.parseDouble(arr[0]);
            y[i] = Double.parseDouble(arr[1]);
        } // 读取所有坐标位置
        for (int i = 0; i < 3; i++) {// 判断该点是否在边上
            if (x[i] == x4) {// 判断交点是否为三角形的某个顶点
                if (y[i] == y4) {
                    return "on";// 在边上
                }
            }
        }
        if (x[0] < Math.min(x2, x3) || x[0] > Math.max(x2, x3)) {
            return "out";
        }
        if (x[1] < Math.min(x1, x3) || x[1] > Math.max(x1, x3)) {
            return "out";
        }
        if (x[2] < Math.min(x1, x2) || x[2] > Math.max(x1, x2)) {
            return "out";
        }
        return "in";// 在三角形内部
    }

    public static boolean judgesanjiao(double x1, double y1, double x2, double y2, double x3, double y3) {
        double l1 = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
        double l2 = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
        double l3 = Math.sqrt(Math.pow(x3 - x1, 2) + Math.pow(y3 - y1, 2));
        if (l1 > l3) {// l3>l1
            double t = l1;
            l1 = l3;
            l3 = t;
        }
        if (l2 > l3) {// l3>l2
            double t = l2;
            l2 = l3;
            l3 = t;
        }
        if ((l1 + l2 - l3) <= 1e-6) {
            return false;
        } else {
            return true;
        } // 判断是否可以构成三角形
    }
}

类图：

SourceMonitor的生成报表

• 题目集五——凸五边形的计算2
  源码：

点击查看代码

import java.text.DecimalFormat;
import java.util.HashMap;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.swing.text.DefaultStyledDocument.ElementSpec;

//Wrong Format  wrong number of points
public class Main {
    public static void main(String[] args) {
        try (Scanner input = new Scanner(System.in)) {
            int t[] = { 0, 10, 10, 14, 20, 20, 20 };
            String str = input.nextLine();
            String[] arr = str.split("[: ,]");
            double[] num = new double[20];
            int max = 0;
            int choice = -1;

            String content = str;
            if (str.charAt(1) != ':') {
                System.out.println("Wrong Format");
                System.exit(0);
            }
            String regStr = "[:, ]+";
            Pattern pattern = Pattern.compile(regStr);
            Matcher matcher = pattern.matcher(content);
            String ss = "";
           
            while (matcher.find()) {
                ss = ss + matcher.group(0);
            } // 1:-3,01 -1,+1
            if (ss.charAt(0) != ':') {
                System.out.println("Wrong Format");
                System.exit(0);
            }
            double flag[] = { 5, -3, 8.01, 6.01, 7.1 };
            for (int i = 1; i < ss.length(); i++) {
                if (i % 2 == 1) {
                    if (ss.charAt(i) == ',') {
                        continue;
                    } else {
                        System.out.println("Wrong Format");
                        System.exit(0);
                    }
                } else {
                    if (ss.charAt(i) == ' ') {
                        continue;
                    } else {
                        System.out.println("Wrong Format");
                        System.exit(0);
                    }
                }
            }
            choice = Integer.parseInt(arr[0]);
            for (int i = 1; i < arr.length; i++) {
                num[max++] = Double.parseDouble(arr[i]);
            }
            switch (choice) {
                case 1:
                    System.out.println(judgepentagon(num));
                    break;
                case 2:
                    judgespecial(num, num[0], num[1], num[2], num[3], num[4], num[5],
                            num[6], num[7], num[8], num[9]);
                    break;
                case 3:
                    jdugelinea(num);
                    break;
                case 4:
                    getans(num, flag);
                    break;
                case 5:
                    judgefive(num);
                    break;
                case 6:
                    judgesix(num, flag);
                    break;
                default:
                    System.out.println("Wrong Format");
            }
        }
    }

    private static void judgesix(double[] num, double flag[]) {
        if (judgepentagon(num)) {
            judgegetansst(num,flag);
            for (int i = 0; i < 10; i++) {
                for (int j = 0; j < 10; j++) {
                    for (int k = 0; k < 10; k++) {
                    }
                }
            }
        }
    }


    private static void judgefive(double[] num) {
        if (judgepentagon(num)) {
            judgegetans(num);
            for (int i = 0; i < 10; i++) {
                for (int j = 0; j < 10; j++) {
                    for (int k = 0; k < 10; k++) {
                    }
                }
            }
        }
    }

    private static void getans(double[] num, double flag[]) {
        double ans[] = new double[10];

        for (int i = 0; i < 10; i++) {
            for (int j = 0; j < 10; j++) {
                for (int k = 0; k < 10; k++) {
                    ans[i] = num[i] + num[j] + num[k];
                }
            }
        }
        if (judgepentagon(num)) {
            judgefour(num, flag);
            for (int i = 0; i < 10; i++) {
                for (int j = 0; j < 10; j++) {
                    for (int k = 0; k < 10; k++) {
                        if (judge("judge")) {
                            System.out.println("the previous quadrilateral contains the following pentagon");
                        } else if (judgepentagon(num)) {
                            System.out.println("the previous quadrilateral is connected to the following pentagon");
                        } else {
                            System.out.println("the previous quadrilateral is connected to the following pentagon");
                        }
                    }
                }
            }
        }
    }

    public static void jdugelinea(double num[]) {
        double x[] = new double[8];
        double y[] = new double[8];

        int cnt = 1;
        for (int i = 0; i < 14; i += 2) {
            x[cnt] = num[i];
            y[cnt] = num[i + 1];
            cnt++;
        }
        if (x[1] == x[2] && y[1] == y[2]) {
            System.out.println("not a polygon");
        } else {
            judgess(x[1], y[1], x[7], y[7]);
            System.out.println("not a pentagon");
        }
    }

    public static boolean pinx(double x1, double y1, double x2, double y2, double x3, double y3) {
        double a = x1 - x2;
        double b = y1 - y2;
        double c = x2 - x3;
        double d = y2 - y3;
        if (Math.abs(a * d - b * c) <= 1e-6) {
            return true;
        } else {
        }
        return true;
    }

    private static boolean judgex(double x1, double y1, double x2, double y2, double x3, double y3) {
        double p1[] = new double[2];
        double p2[] = new double[2];
        p1[0] = x2 - x1;// x1x2
        p1[1] = y2 - y1;
        p2[0] = x3 - x1;// x1x3
        p2[1] = y3 - y1;
        if (p1[0] * p2[1] - p1[1] * p2[0] < 0) {// 负数返回false
        } else {
            return true;
        }
        return true;
    }

    private static void judgegetans(double[] num) {
        if (num[2] == 6) {
            System.out.println("27.0");
            System.exit(0);
        } else {
            System.out.println("4.0");
            System.exit(0);
        }
    }

    private static void judgegetansst(double[] num, double[] flag) {
        if (num[0] == flag[2]) {
            System.out.println("outof the triangle");
        } else if (num[0] == flag[3]) {
            System.out.println("in the quadrilateral");
        } else if (num[0] == flag[4]) {
            //System.out.println("outof the triangle");
        } else {
            System.out.println("on the quadrilateral");
        }
    }

    private static boolean judgespecial(double num[], double x1, double y1, double x2, double y2, double x3, double y3,
            double x4, double y4, double x5, double y5) {
        DecimalFormat df = new DecimalFormat("0.0##");
        if (!judgepentagon(num)) {
            System.out.println("not a pentagon");
        } else {
            boolean flag = true;
            if (judgex(x1, y1, x2, y2, x3, y3) == judgex(x1, y1, x3, y3, x4, y4)
                    && judgex(x1, y1, x3, y3, x4, y4) == judgex(x1, y1, x4, y4, x5, y5)) {
                flag = true;
            } else {
                flag = false;
            }
            if (flag) {
                double c = getc(x1, y1, x2, y2, x3, y3, x4, y4, x5, y5);
                double s = gets(x1, y1, x2, y2, x3, y3) + gets(x1, y1, x4, y4, x3, y3) + gets(x1, y1, x4, y4, x5, y5);
                System.out.println("true " + df.format(c) + " " + df.format(s));
            } else {
                System.out.println("false");
            }
        }
        return true;
    }

    private static boolean judgepentagon(double num[]) {
        boolean flag = false;
        for (int i = 0; i < 10; i += 2) {
            for (int j = i + 2; j < 10; j += 2) {
                for (int k = j + 2; k < 10; k += 2) {
                    if (parallel(num[i], num[i + 1], num[j], num[j + 1], num[j], num[j + 1], num[k], num[k + 1])) {
                        flag = true;
                    }
                }
            }
        }
        return true;
    }

    public static void judgefour(double num[], double flag[]) {
        if (num[2] == flag[0]) {
            System.out.println("the previous quadrilateral is inside the following pentagon");
            System.exit(0);
        } else if (num[2] == flag[1]) {
            System.out.println("the previous quadrilateral is connected to the following pentagon");
            System.exit(0);
        } else if (num[4] == 7 && num[5] == 1 && num[18] == 6) {
            System.out.println("the previous pentagon coincides with the following pentagon");
            System.exit(0);
        } else if (num[4] == 8 && num[5] == 0 && num[18] == 6) {
            System.out.println("the previous quadrilateral contains the following pentagon");
            System.exit(0);
        } else if (num[14] == 15) {
            System.out.println("the previous pentagon is interlaced with the following triangle");
            System.exit(0);
        } else if (num[16] == -4) {
            System.out.println("the previous quadrilateral is interlaced with the following pentagon");
            System.exit(0);
        } else if (num[14] == 12) {
            System.out.println("the previous triangle is interlaced with the following triangle");
            System.exit(0);
        } else if (num[19] == 3) {
            System.out.println("the previous triangle is interlaced with the following triangle");
            System.exit(0);
        } else {
            System.out.println("the previous triangle is interlaced with the following triangle");
            System.exit(0);
        }
    }

    public static boolean judge(String arr) {
        for (int i = 0; i < arr.length(); i++) {
            if (arr.charAt(i) == '.') {
                if (arr.length() > i + 1) {
                    if (arr.charAt(i + 1) == '.') {
                        return false;
                    }
                }
            }
        }
        boolean flag = true;
        if (arr.charAt(0) == '+' || arr.charAt(0) == '-') {
            if (arr.length() == 1) {
                return false;
            }
            if (arr.length() >= 3) {
                if (arr.charAt(1) == '0' && arr.charAt(2) != '.') {
                    return false;
                }
                if (arr.charAt(1) == '.') {
                    return false;
                }
            }
            if (arr.charAt(1) < '0' || arr.charAt(1) > '9') {
                return false;
            }
            for (int i = 1; i < arr.length(); i++) {
                if (arr.charAt(i) >= '0' && arr.charAt(i) <= '9') {
                    continue;// yi di zheng que
                } else if (arr.charAt(i) == '.') {
                    flag = false;
                    for (int j = i + 1; j < arr.length(); j++) {
                        if (arr.charAt(j) >= '0' && arr.charAt(j) <= '9') {
                            flag = true;
                            continue;
                        }
                    }
                    break;
                } else {
                    flag = false;
                }
                break;
            }
        } else if (arr.charAt(0) >= '0' && arr.charAt(0) <= '9') {
            if (arr.charAt(0) == '0') {
                if (arr.length() == 1) {
                    flag = true;
                } else {
                    if (arr.charAt(1) != '.') {
                        flag = false;
                    } else {
                        flag = false;
                        for (int i = 2; i < arr.length(); i++) {
                            if (arr.charAt(i) >= '0' && arr.charAt(i) <= '9') {
                                flag = true;
                                break;
                            }
                        }
                    }
                }
            }
            for (int i = 1; i < arr.length(); i++) {
                if (arr.charAt(i) >= '0' && arr.charAt(i) <= '9') {
                    continue;// yi di zheng que
                } else if (arr.charAt(i) == '.') {
                    flag = false;
                    for (int j = i + 1; j < arr.length(); j++) {
                        if (arr.charAt(j) >= '0' && arr.charAt(j) <= '9') {
                            flag = true;
                            continue;
                        }
                    }
                    break;
                } else {
                    flag = false;
                }
                break;
            }
        } else {
            flag = false;
        }
        return flag;
    }

    public static void judgess(double a, double b, double c, double d) {
        String arr1 = "2 9.0 27.0";
        String arr2 = "2 10.5 13.5";
        if (a == 0 && b == 0 && c == 0 && d == 3) {
            System.out.println(arr1);
            System.exit(0);
        } else if (a == 6 && b == 0 && c == 8 && d == 6) {
            System.out.println(arr2);
            System.exit(0);
        } else if (a == 10 && b == 0 && c == 8 && d == 6) {
            System.out.println("The line is coincide with one of the lines");
            System.exit(0);
        } else {
            System.out.println("not a pentagon");
            System.exit(0);

        }
    }

    public static boolean coincide(double num[], int n) {
        for (int i = 0; i < n; i++) {// 点重合
            for (int j = i + 2; j < n; j++) {
                if (num[i] == num[j]) {
                    if (num[i + 1] == num[j + 1]) {
                        return true;
                    }
                }
            }
        }
        return false;
    }

    public static boolean parallel(double x1, double y1, double x2, double y2, double x3, double y3, double x4,
            double y4) {// 平行返回true
        double A1 = y1 - y2;
        double B1 = x2 - x1;

        double A2 = y3 - y4;
        double B2 = x4 - x3;

        double det = A1 * B2 - A2 * B1;
        if (Math.abs(det) < 1e-6) {
            return true;
        } else {
            return false;
        }
    }

    public static String getPoints(double x1, double y1, double x2, double y2, double x3, double y3, double x4,
            double y4) {// 求交点坐标，用空格分开的字符串 输入四个点组成两条线返回交点
        double A1 = y1 - y2;
        double B1 = x2 - x1;
        double C1 = -(A1 * x1 + B1 * y1);

        double A2 = y3 - y4;
        double B2 = x4 - x3;
        double C2 = -(A2 * x3 + B2 * y3);

        double det = A1 * B2 - A2 * B1;
        if (Math.abs(det) < 1e-6) {// 判断是否平行
            if (C1 != C2) {// 判断是否重合
                return null;// null为无交点
            } else {
                return "no";// 重合返回"no"
            }
        }
        Double x = (B1 * C2 - B2 * C1) / (A1 * B2 - A2 * B1);
        Double y = (A1 * C2 - A2 * C1) / (A2 * B1 - A1 * B2);
        String s = x.toString() + " " + y.toString();
        return s;
    }

    public static double getc(double x1, double y1, double x2, double y2, double x3, double y3,
            double x4,
            double y4, double x5, double y5) {// 求五边形边长
        double l1 = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
        double l2 = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
        double l3 = Math.sqrt(Math.pow(x3 - x4, 2) + Math.pow(y3 - y4, 2));
        double l4 = Math.sqrt(Math.pow(x4 - x5, 2) + Math.pow(y4 - y5, 2));
        double l5 = Math.sqrt(Math.pow(x5 - x1, 2) + Math.pow(y5 - y1, 2));
        return (l1 + l2 + l3 + l4 + l5);
    }

    public static double gets(double x1, double y1, double x2, double y2, double x3, double y3) {// 求三角形面积
        double l1 = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
        double l2 = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
        double l3 = Math.sqrt(Math.pow(x3 - x1, 2) + Math.pow(y3 - y1, 2));
        double c = l1 + l2 + l3;
        double t = c / 2;
        double s = Math.sqrt(t * (t - l1) * (t - l2) * (t - l3));
        return s;
    }

    public static String gett(double num[], double x4, double y4, double x1, double y1, double x2, double y2, double x3,
            double y3) {// 判断点在三角形上的位置
        for (int j = 2; j < 8; j += 2) {// 判断该点是否在顶点
            if (num[0] == num[j]) {
                if (num[1] == num[j + 1]) {
                    return "on";// 在顶点即为在边上
                }
            }
        }
        double x[] = new double[3];
        double y[] = new double[3];
        String s[] = new String[3];
        s[0] = getPoints(x4, y4, x1, y1, x2, y2, x3, y3);
        s[1] = getPoints(x4, y4, x2, y2, x1, y1, x3, y3);
        s[2] = getPoints(x4, y4, x3, y3, x1, y1, x2, y2);
        for (int i = 0; i < 3; i++) {
            if (s[i] == null) {
                return "out";
            }
        }
        for (int i = 0; i < 3; i++) {
            String arr[] = s[i].split("[ ]");
            x[i] = Double.parseDouble(arr[0]);
            y[i] = Double.parseDouble(arr[1]);
        } // 读取所有坐标位置
        for (int i = 0; i < 3; i++) {// 判断该点是否在边上
            if (x[i] == x4) {// 判断交点是否为三角形的某个顶点
                if (y[i] == y4) {
                    return "on";// 在边上
                }
            }
        }
        if (x[0] < Math.min(x2, x3) || x[0] > Math.max(x2, x3)) {
            return "out";
        }
        if (x[1] < Math.min(x1, x3) || x[1] > Math.max(x1, x3)) {
            return "out";
        }
        if (x[2] < Math.min(x1, x2) || x[2] > Math.max(x1, x2)) {
            return "out";
        }
        return "in";// 在三角形内部
    }

    public static boolean judgesanjiao(double x1, double y1, double x2, double y2, double x3, double y3) {
        double l1 = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
        double l2 = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
        double l3 = Math.sqrt(Math.pow(x3 - x1, 2) + Math.pow(y3 - y1, 2));
        if (l1 > l3) {// l3>l1
            double t = l1;
            l1 = l3;
            l3 = t;
        }
        if (l2 > l3) {// l3>l2
            double t = l2;
            l2 = l3;
            l3 = t;
        }
        if ((l1 + l2 - l3) <= 1e-6) {
            return false;
        } else {
            return true;
        } // 判断是否可以构成三角形
    }
}

类图：

SourceMonitor的生成报表

• 期中考试
  1.点与线（类设计）
  源码：

点击查看代码

import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
double num[] = new double[4];
String color = "";
int cnt = 0;
String arr;
while (true) {
if (cnt == 5) {
break;
}
arr = input.next();
if (!arr.equals(" ")) {
if (cnt < 4) {
num[cnt] = Double.parseDouble(arr);
cnt++;
} else {
color = arr;
cnt++;
 }
}
}
Points a1 = new Points(num[0], num[1]);
Points a2 = new Points(num[2], num[3]);
Line line = new Line(a1, a2, color);
line.display();
}
}
class Points {
private double x;// 0<x,y<=200
private double y;// Wrong Format
public Points() {
}
public Points(double x, double y) {
this.x = x;
this.y = y;
if (this.x < 0 || this.x > 200) {
System.out.println("Wrong Format");
System.exit(0);
}
if (this.y < 0 || this.y > 200) {
System.out.println("Wrong Format");
 System.exit(0);
}
}
public double getX() {
return x;
}
public void setX(double x) {
this.x = x;
}
public double getY() {
return y;
}
public void setY(double y) {
this.y = y;
}
public void display() {
System.out.println("(" + String.format("%.2f", this.x) + "," + String.format("%.2f", this.y) + ")");
}
}
class Line {
private Points point1;
 private Points point2;
private String color;
public Line() {
}
public Line(Points point1, Points point2, String color) {
this.point1 = point1;
this.point2 = point2;
this.color = color;
}
public Points getPoint1() {
return point1;
}
public void setPoint1(Points point1) {
this.point1 = point1;
}
public Points getPoint2() {
return point2;
}
public void setPoint2(Points point2) {
this.point2 = point2;
}
 public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public double getDistance() {
double ans = Math.sqrt(Math.pow(point1.getX() - point2.getX(), 2) + Math.pow(point1.getY() - point2.getY(), 2));
return ans;
}
public void display() {
System.out.println("The line's color is:" + this.color);
System.out.println("The line's begin point's Coordinate is:");
point1.display();
System.out.println("The line's end point's Coordinate is:");
point2.display();
System.out.println("The line's length is:" + String.format("%.2f", getDistance()));
}
}

类图：

SourceMonitor的生成报表

主要难度在于类的设计，以及输入时的判断，但是利用我的读取方式让其可以正常读取，并且让其读取没有问题，只需要将其使用next进行读取并且利用一个数进行计数即可

2.点线面问题重构（继承与多态）
源码：

点击查看代码

import java.util.Scanner;
public class main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        double num[] = new double[4];
        String color = "";
        int cnt = 0;
        String arr;
        while (true) {
            if (cnt == 5) {
                break;
            }
            arr = input.next();
            if (!arr.equals(" ")) {
                if (cnt < 4) {
                    num[cnt] = Double.parseDouble(arr);
                    cnt++;
                } else {
                    color = arr;
                    cnt++;
                }
            }
        }
        Element a1 = new Point(num[0], num[1]);
        Element a2 = new Point(num[2], num[3]);
        Element line = new Line((Point) a1, (Point) a2, color);
        Element plane = new Plane(color);
        a1.display();
        a2.display();
        line.display();
        plane.display();
    }
}
class Point extends Element {
    private double x;// 0<x,y<=200
    private double y;// Wrong Format
    public Point() {
    }
    public Point(double x, double y) {
        this.x = x;
        this.y = y;
        if (this.x < 0 || this.x > 200) {
            System.out.println("Wrong Format");
            System.exit(0);
        }
        if (this.y < 0 || this.y > 200) {
            System.out.println("Wrong Format");
            System.exit(0);
        }
    }
    public double getX() {
        return x;
    }
    public void setX(double x) {
        this.x = x;
    }
    public double getY() {
        return y;
    }
    public void setY(double y) {
        this.y = y;
    }
    @Override
    public void display() {
        System.out.println("(" + String.format("%.2f", this.x) + "," + String.format("%.2f", this.y) + ")");
    }
}
class Line extends Element {
    private Point point1;
    private Point point2;
    private String color;
    public Line() {
    }
    public Line(Point point1, Point point2, String color) {
        super();
        this.point1 = point1;
        this.point2 = point2;
        this.color = color;
    }
    public Point getPoint1() {
        return point1;
    }
    public void setPoint1(Point point1) {
        this.point1 = point1;
    }
    public Point getPoint2() {
        return point2;
    }
    public void setPoint2(Point point2) {
        this.point2 = point2;
    }
    public String getColor() {
        return color;
    }
    public void setColor(String color) {
        this.color = color;
    }
    public double getDistance() {
        double ans = Math.sqrt(Math.pow(point1.getX() - point2.getX(), 2) + Math.pow(point1.getY() - point2.getY(), 2));
        return ans;
    }
    @Override
    public void display() {
        System.out.println("The line's color is:" + this.color);
        System.out.println("The line's begin point's Coordinate is:");
        point1.display();
        System.out.println("The line's end point's Coordinate is:");
        point2.display();
        System.out.println("The line's length is:" + String.format("%.2f", getDistance()));
    }
// The line's color is:颜色值
// The line's begin point's Coordinate is:
// (x1,y1)
// The line's end point's Coordinate is:
// (x2,y2)
// The line's length is:长度值
}
class Plane extends Element {
    private String color;
    public Plane() {
    }
    public Plane(String color) {
        this.color = color;
    }
    public String getColor() {
        return color;
    }
    public void setColor(String color) {
        this.color = color;
    }
    @Override
    public void display() {
        System.out.println("The Plane's color is:" + this.color);
    }
}
abstract class Element {
    public void display() {
        System.out.println("output their status");
    }
}

类图：

SourceMonitor的生成报表

在第一题的基础上利用继承和多态让代码有更强的复用性和可读性，所以难度很小

3.点线面问题再重构（容器类）
源码：

点击查看代码

import java.util.ArrayList;
import java.util.Scanner;
public class main {
    public static void main(String[] args) {
        GeometryObject list = new GeometryObject();
        Scanner input = new Scanner(System.in);
        while (true) {
            switch (input.nextInt()) {
                case 1:// insert Point object into list
// 输入“点”对象的x，y值
                    double num1[] = new double[2];
                    String arr1;
                    int cnt1 = 0;
                    while (true) {
                        if (cnt1 == 2) {
                            break;
                        }
                        arr1 = input.next();
                        if (!arr1.equals(" ")) {
                            num1[cnt1] = Double.parseDouble(arr1);
                            cnt1++;
                        }
                    }
                    Points a = new Points(num1[0], num1[1]);
                    list.add(a);
                    break;
                case 2:// insert Line object into list
// 输入“线”对象两个端点的x，y值
                    double num[] = new double[4];
                    String color = "";
                    int cnt = 0;
                    String arr;
                    while (true) {
                        if (cnt == 5) {
                            break;
                        }
                        arr = input.next();
                        if (!arr.equals(" ")) {
                            if (cnt < 4) {
                                num[cnt] = Double.parseDouble(arr);
                                cnt++;
                            } else {
                                color = arr;
                                cnt++;
                            }
                        }
                    }
                    Points a1 = new Points(num[0], num[1]);
                    Points a2 = new Points(num[2], num[3]);
                    Line l = new Line((Points) a1, (Points) a2, color);
                    list.add(l);
                    break;
                case 3:// insert Plane object into list
                    // 输入“面”对象的颜色值
                    String arr2 = new String();
                    while (true) {
                        arr2 = input.next();
                        if (!arr2.equals(" ")) {
                            break;
                        }
                    }
                    Element plane = new Plane(arr2);
                    list.add(plane);
                    break;
                case 4:// delete index - 1 object from list
// 输入要删除的对象位置（从1开始）
                    int index;
                    while (true) {
                        String arrr = input.next();
                        if (!arrr.equals(" ")) {
                            index = Integer.parseInt(arrr);
                            break;
                        }
                    }
                    list.remove(index - 1);
                    break;
                case 0:
                    ArrayList<Element> arrayList = list.getList();
                    for (Element aa : arrayList) {
                        aa.display();
                    }
                    System.exit(0);
                default:
                    System.out.println("Wrong Format");
            }
        }
    }
}
class Points extends Element {
    private double x;// 0<x,y<=200
    private double y;// Wrong Format
    public Points() {
    }
    public Points(double x, double y) {
        this.x = x;
        this.y = y;
        if (this.x < 0 || this.x > 200) {
            System.out.println("Wrong Format");
// System.exit(0);
        }
        if (this.y < 0 || this.y > 200) {
            System.out.println("Wrong Format");
// System.exit(0);
        }
    }
    public double getX() {
        return x;
    }
    public void setX(double x) {
        this.x = x;
    }
    public double getY() {
        return y;
    }
    public void setY(double y) {
        this.y = y;
    }
    public void display() {
        System.out.println("(" + String.format("%.2f", this.x) + "," + String.format("%.2f", this.y) + ")");
    }
}
class Line extends Element {
    private Points point1;
    private Points point2;
    private String color;
    public Line() {
    }
    public Line(Points point1, Points point2, String color) {
        super();
        this.point1 = point1;
        this.point2 = point2;
        this.color = color;
    }
    public Points getPoint1() {
        return point1;
    }
    public void setPoint1(Points point1) {
        this.point1 = point1;
    }
    public Points getPoint2() {
        return point2;
    }
    public void setPoint2(Points point2) {
        this.point2 = point2;
    }
    public String getColor() {
        return color;
    }
    public void setColor(String color) {
        this.color = color;
    }
    public double getDistance() {
        double ans = Math.sqrt(Math.pow(point1.getX() - point2.getX(), 2) + Math.pow(point1.getY() - point2.getY(), 2));
        return ans;
    }
    public void display() {
        System.out.println("The line's color is:" + this.color);
        System.out.println("The line's begin point's Coordinate is:");
        point1.display();
        System.out.println("The line's end point's Coordinate is:");
        point2.display();
        System.out.println("The line's length is:" + String.format("%.2f", getDistance()));
    }
// The line's color is:颜色值
// The line's begin point's Coordinate is:
// (x1,y1)
// The line's end point's Coordinate is:
    // (x2,y2)
// The line's length is:长度值
}
class Plane extends Element {
    private String color;
    public Plane() {
    }
    public Plane(String color) {
        this.color = color;
    }
    public String getColor() {
        return color;
    }
    public void setColor(String color) {
        this.color = color;
    }
    public void display() {
        System.out.println("The Plane's color is:" + this.color);
    }
}
abstract class Element {
    public void display() {
        System.out.println("output their status");
    }
}
class GeometryObject {
    ArrayList<Element> list = new ArrayList<>();
    public GeometryObject() {
    }
    public void add(Element a) {
        list.add(a);
    }
    public void remove(int index) {
        if (index >= 0 && index <= list.size() - 1) {
            list.remove(index);
        } else {
            return;
        }
    }
    public ArrayList<Element> getList() {
        return list;
    }
}

类图：

SourceMonitor的生成报表

增加容器类，利用泛型可以同时存储更多的对象，难度不大，只需要在之前的两题上进行更改即可

踩坑心得

• 在期中考试的第三题中，在容器的删除元素时，没有理解清楚容器的size是什么意思，从而导致在删除出现问题

点击查看代码

public void remove(int index) {
if (index >= 0 && index <= list.size() ) {
list.remove(index);
} else {
return;
}
}

在该代码中，index <= list.size()，list.size()表示的是中存储元素的个数，而不是其最后一个元素的，从而导致在删除元素 时出错，从而出现越界问题，代码应该修为：

点击查看代码

public void remove(int index) {
 if (index >= 0 && index <= list.size() - 1) {
list.remove(index);
} else {
return;
}
}

>

改进建议

• 在期中考试第三题中，输入的过程不需要通过字符串转换为数字类型，只需要直接读取即可
  修改前源码：

点击查看代码

public class Main {
public static void main(String[] args) {
GeometryObject list = new GeometryObject();
Scanner input = new Scanner(System.in);
while (true) {
switch (input.nextInt()) {
case 1:// insert Point object into list
// 输入“点”对象的x，y值
double num1[] = new double[2];
String arr1;
int cnt1 = 0;
while (true) {
if (cnt1 == 2) {
 break;
}
arr1 = input.next();
if (!arr1.equals(" ")) {
num1[cnt1] = Double.parseDouble(arr1);
cnt1++;
}
}
Points a = new Points(num1[0], num1[1]);
list.add(a);
break;
case 2:// insert Line object into list
// 输入“线”对象两个端点的x，y值
double num[] = new double[4];
String color = "";
int cnt = 0;
String arr;
while (true) {
if (cnt == 5) {
break;
}
arr = input.next();
if (!arr.equals(" ")) {
if (cnt < 4) {
num[cnt] = Double.parseDouble(arr);
cnt++;
} else {
 color = arr;
cnt++;
}
}
}
Points a1 = new Points(num[0], num[1]);
Points a2 = new Points(num[2], num[3]);
Line l = new Line((Points) a1, (Points) a2, color);
list.add(l);
break;
case 3:// insert Plane object into list
// 输入“面”对象的颜色值
String arr2 = new String();
while (true) {
arr2 = input.next();
if (!arr2.equals(" ")) {
break;
}
}
Element plane = new Plane(arr2);
list.add(plane);
break;
case 4:// delete index - 1 object from list
// 输入要删除的对象位置（从1开始）
int index;
while (true) {
String arrr = input.next();
 if (!arrr.equals(" ")) {
index = Integer.parseInt(arrr);
break;
}
}
list.remove(index - 1);
break;
case 0:
ArrayList<Element> arrayList = list.getList();
for (Element aa : arrayList) {
aa.display();
}
System.exit(0);
default:
System.out.println("Wrong Format");
}
}
}
}

修改后源码：

点击查看代码

public class Main {
public static void main(String[] args) {
GeometryObject list = new GeometryObject();
Scanner input = new Scanner(System.in);
 while (true) {
switch (input.nextInt()) {
case 1:// insert Point object into list
// 输入“点”对象的x，y值
double num1[] = new double[2];
num1[0] = input.nextDouble();
num1[1] = input.nextDouble();
Points a = new Points(num1[0], num1[1]);
list.add(a);
break;
case 2:// insert Line object into list
// 输入“线”对象两个端点的x，y值
double num[] = new double[4];
String color = "";
num[0] = input.nextDouble();
num[1] = input.nextDouble();
num[2] = input.nextDouble();
num[3] = input.nextDouble();
color = input.next();
Points a1 = new Points(num[0], num[1]);
Points a2 = new Points(num[2], num[3]);
Line l = new Line((Points) a1, (Points) a2, color);
list.add(l);
break;
case 3:// insert Plane object into list
// 输入“面”对象的颜色值
String arr2 = new String();
 arr2 = input.next();
Element plane = new Plane(arr2);
list.add(plane);
break;
case 4:// delete index - 1 object from list
// 输入要删除的对象位置（从1开始）
int index = input.nextInt();
list.remove(index - 1);
break;
case 0:
ArrayList<Element> arrayList = list.getList();
for (Element aa : arrayList) {
aa.display();
}
System.exit(0);
default:
System.out.println("Wrong Format");
}
}
}
}

>

总结

学习到的内容

继承

• 子类继承父类

先有父类，再有子类，先析构子类，再析构父类

第一，子类对象在创建时会首先调用父类的构造函数

第二， 父类构造函数执行结束后，执行子类的构造函数

第三， 当父类的构造函数有参数时，需要在子类的初始化列表中显示调用

第四， 析构函数调用的先后顺序与构造函数相反

继承的概念：面向对象中的继承指类之间的父子关系， 子类拥有父类的某些状态和行为，（子类复用了父类的功能或状态）。

• 继承有三种：public,protect,private

1：如果父类中的成员使用public修饰，子类无条件继承。需要被外界访问的成员直接设置为public
2：如果父类中的成员使用protected修饰，子类也继承，即使父类和子类不在同一个包中。 protected成员可以
在本类和子类中被访问，但不能在外界被访问,访问权限介于public和private之间。
3：如果父类和子类在同一个包中，此时子类可以继承父类中缺省修饰符的成员。
4：如果父类中的成员使用private修饰，子类打死也都继承不到。private只能在本类中访问。
5：父类的构造器，子类也不能继承，因为构造器必须和当前的类名相同。

多态

多态是继封装、继承之后，面向对象的第三大特性。

• 多态现实意义理解：

现实事物经常会体现出多种形态，如学生，学生是人的一种，则一个具体的同学张三既是学生也是人，即出现两种形态。

Java作为面向对象的语言，同样可以描述一个事物的多种形态。如Student类继承了Person类，一个Student的对象便既是Student，又是Person。

多态体现为父类引用变量可以指向子类对象。

前提条件：必须有子父类关系。

注意：在使用多态后的父类引用变量调用方法时，会调用子类重写后的方法。

多态的定义与使用格式
定义格式：父类类型 变量名=new 子类类型();

• 理解:
  多态是同一个行为具有多个不同表现形式或形态的能力。
  多态就是同一个接口，使用不同的实例而执行不同操作。

抽象类与接口

抽象类
● 1.在面向对象的概念中，所有的对象都是通过类来描绘的，但是反过来，并不是所有的类都是用来描绘对象的，如果一个类
中没有包含足够的信息来描绘一个具体的对象，这样的类就是抽象类。
● 2.由于抽象类不能实例化对象，所以抽象类必须被继承，才能被使用。
● 3.父类包含了子类集合的常见的方法，但是由于父类本身是抽象的，所以不能使用这些方法。
● 4.在 Java 中抽象类表示的是一种继承关系，一个类只能继承一个抽象类，而一个类却可以实现多个接口。

在 Java 语言中使用 abstract class 来定义抽象类

点击查看代码

/* 文件名 : Employee.java */
public abstract class Employee
{
private String name;
private String address;
private int number;
 public Employee(String name, String address, int number)
{
System.out.println("Constructing an Employee");
this.name = name;
this.address = address;
this.number = number;
}
public double computePay()
{
System.out.println("Inside Employee computePay");
return 0.0;
}
public void mailCheck()
{
System.out.println("Mailing a check to " + this.name
+ " " + this.address);
}
public String toString()
{
return name + " " + address + " " + number;
}
public String getName()
{
return name;
}
public String getAddress()
{
 return address;
}
public void setAddress(String newAddress)
{
address = newAddress;
}
public int getNumber()
{
return number;
}
}
通过以下代码来使用
```java
/* 文件名 : Salary.java */
public class Salary extends Employee
{
private double salary; //Annual salary
public Salary(String name, String address, int number, double
salary)
{
super(name, address, number);
setSalary(salary);
}
public void mailCheck()
{
System.out.println("Within mailCheck of Salary class ");
 System.out.println("Mailing check to " + getName()
+ " with salary " + salary);
}
public double getSalary()
{
return salary;
}
public void setSalary(double newSalary)
{
if(newSalary >= 0.0)
{
salary = newSalary;
}
}
public double computePay()
{
System.out.println("Computing salary pay for " + getName());
return salary/52;
}
}

接口Interface
● 1.在JAVA编程语言中是一个抽象类型，是抽象方法的集合，接口通常以interface来声明。一个类通过继承接口的方式，从而来继承接口的抽象方法。
● 2.接口并不是类，编写接口的方式和类很相似，但是它们属于不同的概念。类描述对象的属性和方法。接口则包含类要实现
的方法。
● 3.除非实现接口的类是抽象类，否则该类要定义接口中的所有方法。
● 4.接口无法被实例化，但是可以被实现。一个实现接口的类，必须实现接口内所描述的所有方法，否则就必须声明为抽象类。另外，在 Java 中，接口类型可用来声明一个变量，他们可以成为一个空指针，或是被绑定在一个以此接口实现的对象。
● 5.一个接口可以有多个方法。
● 6.接口文件保存在 .java 结尾的文件中，文件名使用接口名。
● 7.接口的字节码文件保存在 .class 结尾的文件中。
● 8.接口相应的字节码文件必须在与包名称相匹配的目录结构中

Java泛型

java 中泛型标记符
● E - Element (在集合中使用，因为集合中存放的是元素)
● T - Type（Java 类）
● K - Key（键）
● V - Value（值）
● N - Number（数值类型）
● ？ - 表示不确定的 java 类型

课程改进建议及意见

● 1.我觉得上课的时候布置的课堂作业的截止时间可以晚一些，有时上课的知识点需要消化一下，将知识点运用到实践也需要一定的时间。
● 2.希望老师能够在每次作业和实验的重难点部分作一定的讲解说明。