面向对象程序设计第一次blog

一、前言

 　　前三次的题目集中主要是关于Java语言的基本程序设计，前两次是熟悉Java语言语法，从最基础的命名变量、选择、循环、函数、字符及字符串到第三次作业的对象和类。题目集一题量较多，但是难度不高，考察的是Java基本语法，根据以前学过的C的知识能够完成，唯一注意的是数据的精度问题以及输入输出的格式问题。题目集二难度适中，考察Java中String的使用。而题目集三虽然题量不大，但是难度却比前两次高得多，初学表示非常艰难，且很多测试点根本想不出来。

　　总而言之，Java是本学期首次接触的语言，存在许多问题不足，还需要多多加强训练这样才能进步

 

二、设计分析

　　1.第二次作业（7-2 串口字符解析）

代码如下：

+ View Code?

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import java.util.Scanner;   public class Main{       public static void main(String[] args) {         // TODO Auto-generated method stub         Scanner in = new Scanner(System.in);         String s = in.nextLine();         int temp = 0;//记录十一位均为1         if(s.length()<11)//小于最小长度         {             System.out.println("null data");             return;         }         for(int i=0;i<11;i++)         {             if(s.charAt(i) == '1')                 temp++;         }         if(temp==11)//输入数据全1，没有起始位         {             System.out.println("null data");             return;         }         if(s.matches("^[1]*$"))         {             System.out.println("null data");             return;         }                   int amount = 1, num = 0,i = 0,a = 0;         boolean flag = false,index = false;         for(i=0; i<s.length()-10;i++)//判断无起始点且数据数不足         {             if(s.charAt(i)=='0')//初始位置             {                 System.out.print(amount+":");                 amount++;                 if(s.charAt(i+10)=='0')//奇偶校验位错误                 {                     flag = false; //                  System.out.println("parity check error");                 }                 else                 {                     num = 0;                     flag = true;                     for(a = i+1; a<i+9;a++)                     {                         if(s.charAt(a)=='1')                         {                             num++;                         }                     }                     if(num%2==0)                     {                         if(s.charAt(i+9)=='1')                             index = true;                         else                             index = false;                     }                     else                     {                         if(s.charAt(i+9)=='0')                             index = true;                         else                             index = false;                     }                 }                 if(flag==true)                 {                     if(index==true)                     {                         for(a=i+1; a<i+9;a++)                             System.out.print(s.charAt(a));//输出                         System.out.print("\n");                     }                     else                     {                         System.out.println("parity check error");//奇偶校验错误                     }                 }                 else                 {                     System.out.println("validate error");//奇偶与结束符错误                 }                 i = i+10;             }         }     } }

　　总结：本题对我来说难度不大，主要在于不同情况下数据读取判断，使用多组for循环来进行读取判断和输出，导致圈复杂度很高

　

　2.第三次作业（7-1 点线形系列1-计算两点之间的距离）

 

　　代码如下：

+ View Code?

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import java.util.Scanner;   public class Main {       public static void main(String[] args) {         // TODO Auto-generated method stub         Scanner in = new Scanner(System.in);         String s = in.nextLine();         int m = 0;//遇到逗号         int n = 0;//遇到空格         int flag = 1;//输入合法性检验         for(int i=0;i<s.length();i++) {             if(s.charAt(i)==',') {                 m++;             }             if(s.charAt(i)==' ') {                 n++;             }             if(s.charAt(i)=='+'||s.charAt(i)=='-'||s.charAt(i)=='.') {                 if(s.charAt(i+1)>='0'&&s.charAt(i+1)<='9') {//合法输入                     continue;                 }                 else {                     flag = 0;                     break;                 }             }         }         if(m-n!=1) {             flag = 0;         }         if(flag == 1) {             if(m!=2) {//坐标点数量超过两个                 System.out.println("wrong number of points");             }             else {                 String []a = new String[4];//存放数据                 for(int i = 0;i<4;i++) {                     a[i] = new String();                 }                                   int p = 0;                 for(int i = 0;i<s.length();i++) {//存放 ，或空格                     if(s.charAt(i)!=' '&&s.charAt(i)!=',') {                         a[p] = a[p] + s.substring(i,i+1);                     }                     else {                         p++;                     }                 }                 int index = 1;                 for(int i = 0;i<4;i++) {//判断每个数字前 + - 是否只有一个                     if(a[i].charAt(0)=='+'||a[i].charAt(0)=='-') {                         if(a[i].charAt(1)=='0'&&a[i].charAt(2)!='.') {                             index = 0;                         }                     }                     else {                         if(a[i].length()>=2) {                             if(a[i].charAt(0)=='0'&&a[i].charAt(1)!='.') {                                 index = 0;                             }                         }                     }                     if(index == 0) {                         break;                     }                 }                 if(index == 0) {                     System.out.println("Wrong Format");                 }                 else{                     double x1,x2,y1,y2;                     x1 = Double.parseDouble(a[0]);                     y1 = Double.parseDouble(a[1]);                     x2 = Double.parseDouble(a[2]);                     y2 = Double.parseDouble(a[3]);                     double distance = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));//计算                     System.out.println(distance);                 }             }         }         else {             System.out.println("Wrong Format");         }     } }

　　总结：这道题的题目要求很简单，就是计算两点间距离，但是它对数据输入输出的格式有很高的要求，如果输入数据不符合坐标形式，程序就要报错提醒，并且也需要格外注意坐标点数量。由于输入数据中包含空格以及逗号，我们输入时应选择字符串输入，并要对数据进行校验。在做好对输入数据的校验后，我用数组进行存放数据，最后通过距离公式来进行计算。此外，本题可以设计一个点类来完成。

 

 　　3.题目三（7-2 点线形系列2-线的计算）

 

 

 代码如下：

+ View Code?

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import java.util.Scanner;   public class Main {       public static void main(String[] args) {         // TODO Auto-generated method stub         Scanner in = new Scanner(System.in);         String s = in.nextLine();         String []arry = new String[20];         String [] str= s.split(":");         int n = str.length;         int j = 0,k = 0;//数组下标         int index = 2;//坐标从第三个字符开始         int flag = 0,temp = 0;         if(n==2){             if(s.charAt(0)<=0&&s.charAt(0)>=6) {                 System.out.println("Wrong Format");                 return;             }             if(s.charAt(1)!=':') {                 System.out.println("Wrong Format");                 return;             }               for(int i=2;i<s.length();i++) {                 if(s.charAt(i)==' ') {                     temp++;                 }                 if(s.charAt(i)==','){                     k++;                 }             }               for(int i=2;i<s.length();i++) {//记录点                 if(s.charAt(i)==','||s.charAt(i)==' ') {                     arry[j] = s.substring(index,i);                     index = i+1;                     j++;                     flag = i;                 }             }               if(k == 2) {//两个点                 arry[3] = s.substring(flag+1,s.length());                 double x1 = Double.parseDouble(arry[0]);                 double y1 = Double.parseDouble(arry[1]);                 double x2 = Double.parseDouble(arry[2]);                 double y2 = Double.parseDouble(arry[3]);                 for(int i=0;i<s.length();i++) {                     if(s.charAt(i)=='1'&&s.charAt(i+1)==':') {                         Point point = new Point(x1,y1,x2,y2);                         point.slope();                     }                     if(temp == 2) {                         System.out.println("wrong number of points");                     }                 }             }             else if(k == 3) {//三个点                 arry[5] = s.substring(flag+1,s.length());                 double x1 = Double.parseDouble(arry[0]);                 double y1 = Double.parseDouble(arry[1]);                 double x2 = Double.parseDouble(arry[2]);                 double y2 = Double.parseDouble(arry[3]);                 double x3 = Double.parseDouble(arry[4]);                 double y3 = Double.parseDouble(arry[5]);                 if(s.charAt(0)=='2') {//选项2                     Point point = new Point(x1,y1,x2,y2,x3,y3);                     point.threepointdistance();                 }                 if(s.charAt(0)=='3') {//选项3                     Point point = new Point(x1,y1,x2,y2,x3,y3);                     point.threepointline();                 }                 if(temp == 3){                     System.out.println("wrong number of points");                 }             }             else if(k == 4) {//四个点                 arry[7] = s.substring(flag+1,s.length());                 double x1 = Double.parseDouble(arry[0]);                 double y1 = Double.parseDouble(arry[1]);                 double x2 = Double.parseDouble(arry[2]);                 double y2 = Double.parseDouble(arry[3]);                 double x3 = Double.parseDouble(arry[4]);                 double y3 = Double.parseDouble(arry[5]);                 double x4 = Double.parseDouble(arry[6]);                 double y4 = Double.parseDouble(arry[7]);                 if(s.charAt(0)=='4') {                     Point point = new Point(x1,y1,x2,y2,x3,y3,x4,y4);                     point.fourpointsparalle();                 }                 if(s.charAt(0)=='5') {                     Point point = new Point(x1,y1,x2,y2,x3,y3,x4,y4);                     point.jiaodian();                 }                 if(temp == 4) {                     System.out.println("wrong number of points");                 }             }             else if(k>4) {//输入点数量不符合要求                 System.out.println("wrong number of points");             }         }       else{           System.out.println("Wrong Format");       }     }  }        class Point {     private double x1,y1,x2,y2,x3,y3,x4,y4;           public Point() {         super();     }           public Point(double x1,double y1,double x2,double y2) {         super();         this.x1 = x1;         this.y1 = y1;         this.x2 = x2;         this.y2 = y2;     }           public Point(double x1,double y1,double x2,double y2,double x3,double y3) {         super();         this.x1 = x1;         this.y1 = y1;         this.x2 = x2;         this.y2 = y2;         this.x3 = x3;         this.y3 = y3;     }           public Point(double x1,double y1,double x2,double y2,double x3,double y3,double x4,double y4) {         super();         this.x1 = x1;         this.y1 = y1;         this.x2 = x2;         this.y2 = y2;         this.x3 = x3;         this.y3 = y3;         this.x4 = x4;         this.y4 = y4;     }           public double getx1() {         return x1;     }           public void setx1(double x1) {         this.x1 = x1;     }           public double gety1() {         return y1;     }           public void sety1(double y1) {         this.y1 = y1;     }           public double getx2() {         return x2;     }           public void setx2(double x2) {         this.x2 = x2;     }           public double gety2() {         return y2;     }           public void sety2(double y2) {         this.y2 = y2;     }           public double getx3() {         return x3;     }           public void setx3(double x3) {         this.x3 = x3;     }           public double gety3() {         return y3;     }           public void sety3(double y3) {         this.y3 = y3;     }           public double getx4() {         return x4;     }           public void setx4(double x4) {         this.x4 = x4;     }           public double gety4() {         return y4;     }           public void sety4(double y4) {         this.y4 = y4;     }           public boolean chonghe(double x1,double y1,double x2,double y2) {//判断两点是否重合         if(x1==x2&&y1==y2) {             return true;         }         else {             return false;         }     }           public void slope() {//斜率         double k = 0;         k = (y1-y2)/(x1-x2);         if(chonghe(x1,y1,x2,y2)) {             System.out.println("points coincide");//两点重合                       }         else {             if(x1==x2) { //分母为0 线条垂直于x轴                 System.out.println("Slope does not exist");                               }             else {                 System.out.println(k);             }         }     }           public void threepointdistance() {//第一个点与另外两条点所成线距离         double distance = Math.abs((y2-y3)*x1+(x3-x2)*y1+x2*y3-y2*x3)/Math.sqrt((y2-y3)*(y2-y3)+(x2-x3)*(x2-x3));         if(!chonghe(x2,y2,x3,y3)) {             System.out.println(distance);         }         else {             System.out.println("points coincide");         }     }           public void threepointline() {         double k1,k2;         k1 = (y1-y2)/(x1-x2);         k2 = (y1-y3)/(x1-x3);         if(!chonghe(x1,y1,x2,y2)&&!chonghe(x1,y1,x3,y3)) {             if(x1==x2&&x1==x3) {                 System.out.println("true");             }             else {                 if(k1==k2) {                     System.out.println("true");                 }                 else {                     System.out.println("false");                 }             }         }         else {             System.out.println("points coincide");         }     }           public void fourpointsparalle() {         if(chonghe(x1,y1,x2,y2)||chonghe(x3,y3,x4,y4)) {             System.out.println("points coincide");         }         else {             if((x1-x2)*(y3-y4)==(y1-y2)*(x3-x4)) {                 System.out.println("true");             }             else {                 System.out.println("false");             }         }     }           public double max(double x1,double x2) {         if(x1>x2) {             return x1;         }         else {             return x2;         }     }           public double min(double x1,double x2) {         if(x1>x2) {             return x2;         }         else {             return x1;         }     }           public boolean isinline(double x,double y) {//判断交点是否在线段上         double max1 = max(x1,x2);         double max2 = max(x3,x4);         double min1 = min(x1,x2);         double min2 = min(x3,x4);         if((x>min1||x>min2)&&(x<max1||x<max2)) {             return true;         }         else {             return false;         }     }           public void jiaodian() {         double k1,k2;         double x,y;         x = (y3*x2*x4-x3*y4*x2-y3*x1*x4+y4*x1*x3-y1*x4*x2+y2*x4*x1+y1*x2*x3-y2*x1*x3)/(x4*y2-x4*y1-x3*y2+x3*y1-x2*y4+x2*y3+x1*y4-x1*y3);         y = (-y2*x4*y3+y2*x3*y4+y3*x4*y1-y4*x3*y1+y4*x2*y1-y1*x2*y3-y4*x1*y2+y2*x1*y3)/(y4*x2-y4*x1-y3*x2+x1*y3-y2*x4+y2*x3+y1*x4-y1*x3);         k1 = (y2-y1)/(x2-x1);         k2 = (y4-y3)/(x4-x3);         if(chonghe(x1,y1,x2,y2)||chonghe(x3,y3,x4,y4)) {             System.out.println("points coincide");         }         else {             if(k1==k2||(x1==x2&&x3==x4)) {                 System.out.println("is parallel lines,have no intersection point");             }             else {                 System.out.println(x+","+y+" "+isinline(x,y));             }         }     } }

　　总结：这道题属于7-1的进阶版，由单纯点的问题转为线的问题，出现四五个点的情况，题目中需求也变得极为多，测试点也极为***钻。这道题我设计点类来对这些需求进行计算，在此之前，还是需要对输入数据进行校验以及处理，要将输入字符拆分存放入数组，采用if判断语句来进行不同要求间算法的求解。但由于我对输入格式的判断存在问题，数据格式的输入测试点过不去，本题没有拿到满分。

SourceMonitor分析图：

 

 

 　　4.作业3（7-3 点线形系列3-三角形的计算）

 

 

 代码如下：

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// package 作业第三题;   import java.util.Scanner;   import java.text.DecimalFormat;   public class Main {       public static void main(String[] args) {         // TODO Auto-generated method stub         Scanner in = new Scanner(System.in);         String s = in.nextLine();         String []arry = new String[20];         int j = 0,k = 0;//数组下标         int index = 2;//坐标从第三个字符开始         int flag = 0,temp = 0;         boolean a = false;         if(s.charAt(0)<=0&&s.charAt(0)>=6) {             System.out.print("Wrong Format");             return;         }                   for(int i=0;i<s.length();i++) {             if(s.charAt(i)==' ') {                 a = true;             }         }           if(s.charAt(1)!=':'||a==false) {             System.out.print("Wrong Format");             return;         }         if(!s.matches("^[1-5][:](([+-]?(0|(0\\.\\d+)|[1-9][0-9]*(\\.\\d+)?))[,]([+-]?(0|(0\\.\\d+)|[1-9][0-9]*(\\.\\d+)?))\\s?)+$")){             System.out.println("Wrong Format");             return;         }                   for(int i=2;i<s.length();i++) {             if(s.charAt(i)==' ') {                 temp++;             }             if(s.charAt(i)==',') {                 k++;             }         }                   for(int i=2;i<s.length();i++) {//记录点             if(s.charAt(i)==','||s.charAt(i)==' ') {                 arry[j] = s.substring(index,i);                 index = i+1;                 j++;                 flag = i;             }         }         if(k == 3) {//三个点             arry[5] = s.substring(flag+1,s.length());             double x1 = Double.parseDouble(arry[0]);             double y1 = Double.parseDouble(arry[1]);             double x2 = Double.parseDouble(arry[2]);             double y2 = Double.parseDouble(arry[3]);             double x3 = Double.parseDouble(arry[4]);             double y3 = Double.parseDouble(arry[5]);             if(s.charAt(0)=='1') {//选项1                 Point point = new Point(x1,y1,x2,y2,x3,y3);                 point.threetriangle();             }             if(s.charAt(0)=='2') {//选项2                 Point point = new Point(x1,y1,x2,y2,x3,y3);                 point.threepointscalculate();             }             if(s.charAt(0)=='3') {//选项3                 Point point = new Point(x1,y1,x2,y2,x3,y3);                 point.panduantriangle();             }         }         else if(k == 4) {//四个点             arry[7] = s.substring(flag+1,s.length());             double x1 = Double.parseDouble(arry[0]);             double y1 = Double.parseDouble(arry[1]);             double x2 = Double.parseDouble(arry[2]);             double y2 = Double.parseDouble(arry[3]);             double x3 = Double.parseDouble(arry[4]);             double y3 = Double.parseDouble(arry[5]);             double x4 = Double.parseDouble(arry[6]);             double y4 = Double.parseDouble(arry[7]);             if(s.charAt(0)=='5') {//选项五                 Point point = new Point(x1,y1,x2,y2,x3,y3,x4,y4);                 point.             }         }         else if(k == 5) { //五个点             arry[9] = s.substring(flag+1,s.length());             double x1 = Double.parseDouble(arry[0]);             double y1 = Double.parseDouble(arry[1]);             double x2 = Double.parseDouble(arry[2]);             double y2 = Double.parseDouble(arry[3]);             double x3 = Double.parseDouble(arry[4]);             double y3 = Double.parseDouble(arry[5]);             double x4 = Double.parseDouble(arry[6]);             double y4 = Double.parseDouble(arry[7]);             double x5 = Double.parseDouble(arry[8]);             double y5 = Double.parseDouble(arry[9]);             if(s.charAt(0)=='4') {//选项四                 Point point = new Point(x1,y1,x2,y2,x3,y3,x4,y4,x5,y5);                 point.fivepointstriangle();             }         }         else if(k>5) {             System.out.println("wrong number of points");         }     } }   // package 作业第三题;   // import java.text.DecimalFormat;   class Point {     private double x1,y1,x2,y2,x3,y3,x4,y4,x5,y5;     private double x,y;           public Point() {         super();     }           public Point(double x1,double y1,double x2,double y2) {         super();         this.x1 = x1;         this.y1 = y1;         this.x2 = x2;         this.y2 = y2;     }     public Point(double x1,double y1,double x2,double y2,double x3,double y3) {         super();         this.x1 = x1;         this.y1 = y1;         this.x2 = x2;         this.y2 = y2;         this.x3 = x3;         this.y3 = y3;     }           public Point(double x1,double y1,double x2,double y2,double x3,double y3,double x4,double y4) {         super();         this.x1 = x1;         this.y1 = y1;         this.x2 = x2;         this.y2 = y2;         this.x3 = x3;         this.y3 = y3;         this.x4 = x4;         this.y4 = y4;     }     public Point(double x1,double y1,double x2,double y2,double x3,double y3,double x4,double y4,double x5,double y5) {         super();         this.x1 = x1;         this.y1 = y1;         this.x2 = x2;         this.y2 = y2;         this.x3 = x3;         this.y3 = y3;         this.x4 = x4;         this.y4 = y4;         this.x5 = x5;         this.y5 = y5;     }     public double getx1() {         return x1;     }           public void setx1(double x1) {         this.x1 = x1;     }           public double gety1() {         return y1;     }           public void sety1(double y1) {         this.y1 = y1;     }           public double getx2() {         return x2;     }           public void setx2(double x2) {         this.x2 = x2;     }           public double gety2() {         return y2;     }           public void sety2(double y2) {         this.y2 = y2;     }           public double getx3() {         return x3;     }           public void setx3(double x3) {         this.x3 = x3;     }           public double gety3() {         return y3;     }           public void sety3(double y3) {         this.y3 = y3;     }           public double getx4() {         return x4;     }           public void setx4(double x4) {         this.x4 = x4;     }           public double gety4() {         return y4;     }           public void sety4(double y4) {         this.y4 = y4;     }           public double getx5() {         return x5;     }           public void setx5(double x5) {         this.x5 = x5;     }           public double gety5() {         return y5;     }           public void sety5(double y5) {         this.y5 = y5;     }           public boolean chonghe(double x1,double y1,double x2,double y2) {//判断两点是否重合         if(x1==x2&&y1==y2) {             return true;         }         else {             return false;         }     }           public boolean triangle(double x1,double y1,double x2,double y2,double x3,double y3) {//判断是否为三角形         double a,b,c;         a = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));         b = Math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));         c = Math.sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));         if(a+b>c&&a+c>b&&b+c>a) {             return true;         }         else {             return false;         }     }           public void threetriangle() {         double a,b,c;         a = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));         b = Math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));         c = Math.sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));         if(!triangle(x1,y1,x2,y2,x3,y3)) {             System.out.println("data error");         }         else {             if(a==b||a==c||b==c) {                 System.out.print("true");             }             else {                 System.out.print("false");             }             System.out.print(" ");             if(a==b&&a==c&&b==c) {                 System.out.print("true");             }             else {                 System.out.print("false");             }         }     }           public void threepointscalculate() {         double a,b,c;         a = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));         b = Math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));         c = Math.sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));         double C = a+b+c;//周长         double S = Math.sqrt((C/2)*(C/2-a)*(C/2-b)*(C/2-c));//面积         double X = (x1+x2+x3)/3;         double Y = (y1+y2+y3)/3;         if(!triangle(x1,y1,x2,y2,x3,y3)) {             System.out.println("data error");         }         else { //          System.out.println(C+" "+S+" "+X+","+Y); //          System.out.printf("%.6f %.6f %.6f %.6f",C,S,X,Y); //          System.out.print(C); //          System.out.print(" "); //          System.out.print(S); //          System.out.print(" "); //          System.out.print(X); //          System.out.print(","); //          System.out.print(Y);             System.out.printf(new DecimalFormat("0.0#####").format(C));             System.out.print(" ");             System.out.printf(new DecimalFormat("0.0#####").format(S));             System.out.print(" ");             System.out.printf(new DecimalFormat("0.0#####").format(X));             System.out.print(",");             System.out.printf(new DecimalFormat("0.0#####").format(Y));         }     }     public void panduantriangle() {         double a,b,c,A,B,C;         a = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));         b = Math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));         c = Math.sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));         A = (b*b+c*c-a*a)/(2*b*c);         B = (a*a+c*c-b*b)/(2*a*c);         C = (b*b+a*a-c*c)/(2*b*a);         if(A>0&&B>0&&C>0) {             System.out.println("false false true");//锐角             return;         }         else if((Math.abs(b*b+c*c-a*a)<=0.000001)||(Math.abs(a*a+c*c-b*b)<=0.000001)||(Math.abs(b*b+a*a-c*c)<=0.000001)) {             System.out.println("false true false");//直角             return;         }         else {             System.out.println("true false false");//钝角             return;         }     }           public void jiaodian() {         double k1,k2,a1= 0,b1 = 0,c1 = 0,S1 = 0,S2 = 0,C = 0,B = 0,A = 0;         double X1,Y1,X2,Y2;         X1 = (y3*x2*x4-x3*y4*x2-y3*x1*x4+y4*x1*x3-y1*x4*x2+y2*x4*x1+y1*x2*x3-y2*x1*x3)/(x4*y2-x4*y1-x3*y2+x3*y1-x2*y4+x2*y3+x1*y4-x1*y3);         Y1 = (-y2*x4*y3+y2*x3*y4+y3*x4*y1-y4*x3*y1+y4*x2*y1-y1*x2*y3-y4*x1*y2+y2*x1*y3)/(y4*x2-y4*x1-y3*x2+x1*y3-y2*x4+y2*x3+y1*x4-y1*x3);         X2 = (y3*x2*x5-x3*y5*x2-y3*x1*x5+y5*x1*x3-y1*x5*x2+y2*x5*x1+y1*x2*x3-y2*x1*x3)/(x5*y2-x5*y1-x3*y2+x3*y1-x2*y5+x2*y3+x1*y5-x1*y3);         Y2 = (-y2*x5*y3+y2*x3*y5+y3*x5*y1-y5*x3*y1+y5*x2*y1-y1*x2*y3-y5*x1*y2+y2*x1*y3)/(y5*x2-y5*x1-y3*x2+x1*y3-y2*x5+y2*x3+y1*x5-y1*x3);         k1 = (y2-y1)/(x2-x1);         k2 = (y4-y3)/(x4-x3);         if(chonghe(x1,y1,x2,y2)||chonghe(x3,y3,x4,y4)) {             System.out.println("points coincide");         }         else {             if(k1==k2||(x1==x2&&x3==x4)) {                 return;             }             else { //              System.out.println(x+","+y+" "+isinline(x,y));                 a1 = Math.sqrt((x3-X1)*(x3-X1)+(y3-Y1)*(y3-Y1));                 b1 = Math.sqrt((x3-X2)*(x3-X2)+(y3-Y2)*(y3-Y2));                 c1 = Math.sqrt((X1-X2)*(X1-X2)+(Y1-Y2)*(Y1-Y2));                 A = Math.sqrt((x4-x5)*(x4-x5)+(y4-y5)*(y4-y5));                 B = Math.sqrt((x3-x5)*(x3-x5)+(y3-y5)*(y3-y5));                 C = Math.sqrt((x3-x4)*(x3-x4)+(y3-y4)*(y3-y4));                 S1 = 0.5 * a1 * b1 * Math.sqrt(1-((b1*b1+c1*c1-a1*a1)/2*b1*c1)*((b1*b1+c1*c1-a1*a1)/2*b1*c1));                 S2 = 0.5 * B * C * Math.sqrt(1-((B*B+C*C-A*A)/2*B*C)*((B*B+C*C-A*A)/2*B*C));                 if(S1<S2)                     System.out.println("2 "+S1+" "+S2);                 else                     System.out.println("2 "+S2+" "+S1);             }         }     }               public void fivepointstriangle() { //      double a,b,c,x,y,X,Y;         boolean judge = false; //      a = Math.sqrt((x3-x4)*(x3-x4)+(y3-y4)*(y3-y4)); //      b = Math.sqrt((x3-x5)*(x3-x5)+(y3-y5)*(y3-y5)); //      c = Math.sqrt((x4-x5)*(x4-x5)+(y4-y5)*(y4-y5));         if(x1==x2&&y1==y2)             System.out.print("points coincide");         else {             if((x3==x4&&y3==y4)||(x3==x5&&y3==y5)||(x4==x5&&y4==y5)||(x3==x4&&x3==x5))                 judge=false;             else {                 if(x3==x4||x3==x5||x4==x5)                     judge=true;                 else {                     double slope1=(y3-y4)/(x3-x4);                     double slope2=(y3-y5)/(x3-x5);                     if(slope1!=slope2)                         judge=true;                 }             }             if(judge) {                 double distance1=((y1-y2)*x3+(x2-x1)*y3+x1*y2-y1*x2)/Math.sqrt((y1-y2)*(y1-y2)+(x1-x2)*(x1-x2));                 double distance2=((y1-y2)*x4+(x2-x1)*y4+x1*y2-y1*x2)/Math.sqrt((y1-y2)*(y1-y2)+(x1-x2)*(x1-x2));                 double distance3=((y1-y2)*x5+(x2-x1)*y5+x1*y2-y1*x2)/Math.sqrt((y1-y2)*(y1-y2)+(x1-x2)*(x1-x2));                 if((distance1>0&&distance2>0&&distance3>0)||(distance1<0&&distance2<0&&distance3<0))                     System.out.print("0");                 else if((distance1==0&&distance2*distance3>0)||(distance2==0&&distance1*distance3>0)||(distance3==0&&distance1*distance2>0))                     System.out.print("1");                 else if((distance1==0&&distance2==0)||(distance1==0&&distance3==0)||(distance2==0&&distance3==0))                     System.out.print("The point is on the edge of the triangle");                 else {                     jiaodian();                   }             }             else                 System.out.print("data error");         }     }           public void fourpoints(){               }     public void input(double a,double b) {         x = a;         y = b;     }         //读取x的值//     public double read_x() {         return x;     }         //读取y的值//     public double read_y() {         return y;     }         //计算两点的距离//     public double caluate_distance(Point p) {         return Math.sqrt((x-p.x )*(x-p.x )+(y-p.y )*(y-p.y));     }         //检查线的两点是否重合//     public boolean chack_point(Point p) {         boolean wssa = false ;         if(Math.abs(x-p.read_x())<1e-15&&Math.abs(y-p.read_y())<1e-15) {             wssa = true ;         }         return wssa;     }   } class Line {     Point p1 = new Point();     Point p2 = new Point();           //检查线段的斜率是否存在//     public boolean chack_slope() {     boolean wssa = true ;     if(Math.abs(p1.read_x()-p2.read_x())<1e-15) {     wssa = false ;     }     return wssa;     }       //计算线段的斜率//     public double caluate_slope() {     return (p1.read_x()-p2.read_y())/(p1.read_x()-p2.read_y());     }           //计算点到直线的距离//     public double caluate_distance(Point a) {     double distance ;     if(if_on_line(a)){         distance = 0;     }     else {         distance = Math.abs(a.read_x()*p1.read_y()+p1.read_x()*p2.read_y()+p2.read_x()*a.read_y()-a.read_x()*p2.read_y()-p1.read_x()*a.read_y()-p2.read_x()*p1.read_y())/p1.caluate_distance(p2);     }     return distance ;     }           //判断点是否再直线上//     public boolean if_on_line(Point p) {         boolean jes = false ;         Line l1 = new Line();         Line l2 = new Line();         l1.p1 = p1;         l1.p2 = p;         l2.p1 = p2;         l2.p2 = p;         if(l1.caluate_slope()==l2.caluate_slope()) {             jes = true;         }         return jes;     }       //判断点是否在线段内//     //在线段内返回true，在线段外返回false//     public boolean if_in_line(Point p) {         boolean jes = true ;         if(p.caluate_distance(p1)>p1.caluate_distance(p2)||p.caluate_distance(p2)>p1.caluate_distance(p2)) {             jes = false ;         }         return jes;     }         //判断两直线是否平行//     //若两直线平行返回1，若两直线重合返回0，若两直线相交返回-1     public int if_parallel(Line l) {         int cnt ;         double x1 = (p1.read_x()-p2.read_x())*(l.p1.read_x()-l.p2.read_x())+(p1.read_y()-p2.read_y())*(l.p1.read_y()-l.p2.read_y());         if(x1/(p1.caluate_distance(p2)*l.p1.caluate_distance(p2))!=1) {             cnt=-1;         }         else {             if(l.caluate_distance(p1)==0) {                 cnt=0;             }             else {                 cnt=1;             }         }         return cnt;     }         //计算两直线交点,返回Point//     public Point caluate_intersection(Line a){         Point p = new Point();         double dx1 = p1.read_x()-p2.read_x();         double dx2 = a.p1.read_x()-a.p2.read_x();         double dy1 = p1.read_x()-p2.read_x();         double dy2 = a.p1.read_x()-a.p2.read_x();         double mid1 = dy1/dx1;         double mid2 = dy2/dx2;         double rx = (a.p2.read_y()-p2.read_y()-a.p2.read_y()*mid2+p2.read_y()*mid1)/(mid1-mid2);         double ry = (rx-p2.read_x())*mid1+p2.read_y();         p.input(rx, ry);         return p;     } } class Triangle {     Point p1 = new Point();     Point p2 = new Point();     Point p3 = new Point();         //检查三点是否构成三角形//     //若构成三角形返回false,若不构成三角形返回true//     public boolean chack_triangle() {         boolean err = true ;         if(Math.abs(p1.caluate_distance(p2)-p1.caluate_distance(p3))<p2.caluate_distance(p3)&&Math.abs(p1.caluate_distance(p3)+p1.caluate_distance(p2))>p2.caluate_distance(p3)){             err = false ;         }         return err ;     }         //判断是否为等边三角形，或等腰三角形//     //若为等腰三角形，返回0//     //若为等边三角形，返回1//     public int shape_line_triangle() {         int shape = 0;         if(Math.abs(p1.caluate_distance(p2)-p1.caluate_distance(p3))<1e-15&&Math.abs(p2.caluate_distance(p1)-p2.caluate_distance(p3))<1e-15) {             shape = 1;         }         return shape;     }       //计算三角形面积,返回面积//     public double caluate_S() {         return Math.abs(p1.read_x()*p2.read_y()+p2.read_x()*p3.read_y()+p3.read_x()*p1.read_y()-p1.read_x()*p3.read_y()-p2.read_x()*p1.read_y()-p3.read_x()*p2.read_y())/2;     }           //计算三角形的周长，返回周长//     public double caluate_C() {         return p1.caluate_distance(p2)+p1.caluate_distance(p3)+p2.caluate_distance(p3);     }           //计算三角形的重心坐标，返回Point//     public Point caluate_gravity_point() {         Point p = new Point();         double dx = (p1.read_x()+p2.read_x()+p3.read_x())/3;         double dy = (p1.read_y()+p2.read_y()+p3.read_y())/3;         p.input(dx, dy);         return p;     }         //判断三角形是锐角三角形还是直角三角形或钝角三角形//     //若是锐角三角形返回1，若是直角三角形返回0，若是钝角三角形则返回-1//     public int shape_horn_triangle() {         int shape ;         double j1 = (p2.read_x()-p1.read_x())*(p3.read_x()-p1.read_x())+(p2.read_y()-p1.read_y())*(p3.read_y()-p1.read_y());         double j2 = (p3.read_x()-p2.read_x())*(p1.read_x()-p2.read_x())+(p3.read_y()-p2.read_y())*(p1.read_y()-p2.read_y());         double j3 = (p1.read_x()-p3.read_x())*(p2.read_x()-p3.read_y())+(p1.read_y()-p3.read_y())*(p2.read_y()-p3.read_y());         if(j1<0||j2<0||j3<0) {             shape = 1;         }         else if(j1==0||j2==0||j3==0) {             shape = 0 ;         }         else {             shape = -1;         }         return shape;     }         //计算直线与三角形的交点//     //返回交点个数//     public int caluate_sum_intersection(Line a) {     int sum = 0;     Line l1 = new Line();     l1.p1=p1;l1.p2=p2;     Line l2 = new Line();     l2.p1=p1;l2.p2=p3;     Line l3 = new Line();     l3.p1=p2;l3.p2=p3;     if(l1.if_parallel(a)==1) {         Point point1 = a.caluate_intersection(l2);         if(l2.if_in_line(point1)) {             sum++;         }         Point point2 = a.caluate_intersection(l3);         if(l3.if_in_line(point2)) {             sum++;         }     }     else if(l2.if_parallel(a)==1) {         Point point1 = a.caluate_intersection(l1);         if(l1.if_in_line(point1)) {             sum++;         }         Point point2 = a.caluate_intersection(l3);         if(l3.if_in_line(point2)) {             sum++;         }     }     else if(l3.if_parallel(a)==1) {         Point point1 = a.caluate_intersection(l1);         if(l1.if_in_line(point1)) {             sum++;         }         Point point2 = a.caluate_intersection(l2);         if(l2.if_in_line(point2)&&point1.chack_point(point2)) {             sum++;         }     }     else {         Point point1 = a.caluate_intersection(l1);         if(l1.if_in_line(point1)) {             sum++;         }         Point point2 = a.caluate_intersection(l2);         if(l2.if_in_line(point2)&&point1.chack_point(point2)) {             sum++;         }         Point point3 = a.caluate_intersection(l2);         if(l2.if_in_line(point3)&&point1.chack_point(point3)&&point2.chack_point(point3)) {         sum++;         }     }     return sum;     }         //判断点是否再三角形内部//     public boolean if_inside(Point a) {         boolean rea = false ;         Line l1 = new Line();         l1.p1=p1;         l1.p2=a;         Line l2 = new Line();         l2.p1=p2;         l2.p2=a;         Line l3 = new Line();         l3.p1=p3;         l3.p2=a;         Line l4 = new Line();         l4.p1=p1;         l4.p2=p2;         Line l5 = new Line();         l5.p1=p2;         l5.p2=p3;         Line l6 = new Line();         l6.p1=p3;         l6.p2=p1;         if(!l5.if_in_line(l1.caluate_intersection(l5))||!l4.if_in_line(l3.caluate_intersection(l4))||!l6.if_in_line(l2.caluate_intersection(l6))) {             rea = true;         }         return rea;     } }

　　总结：一开始写这道题时，想着只用点类来进行，但是在最后两个需求上，单用点类非常难实现，在前面进行字符串分割，以及前三个需求时，点类可以用的很简单，但是到了四五需求，不知道该如何设计方法，参数传递彻底搞晕，最后也尝试设计线类以及三角形类，但还是没能完成该题。

SourceMonitor分析图：

 

 

三、踩坑心得

　　1.这四道题我并没有全拿满分，有部分题目的部分测试点过不去，在字符串的处理上有很多地方做的不好，导致输入数据格式存在错误。

　　2.对类的认识还不是很充分，有很多在Main中的其实可以将其封装，导致代码冗长易出错

　　3.在计算上不是数学上的范围，例如判断直角三角形，应该是两边平方和减第三边平方小于一个极小值，而不是等于0，题目中就有一个测试点是关于此的，我改了很久。

　　4.不要怕麻烦，无论是学习正则表达式还是去多设计类，能用类的就用类，到后期会越来越方便。

 

四、改进建议

　　1.switch语句的复杂度比if语句更低，在之后的编码中能用switch替代就尽量不使用if。

　　2.编写代码前提前构建好类图，效率更高

　　3.多用类，多用方法，不要一直Main

　　4.String类型判断使用正则表达式很快

　　5.边写代码边调试，多写注释

 

五、总结

　　第一阶段的学习已经过去，我逐渐明白Java和c的相似以及不同，基本语法虽大体相同，但角度却不同了。我更熟练的运用字符串及其相关函数，并且慢慢习惯运用方法和类，但是并不熟练。对于整体的题目设计方面还需要大大加强，这样才能简化运算以及代码，可读性也会更强。另外，一定要合理规划好时间，不要拖拉，作业发布最好就快速开始，遇到问题积极寻求帮助，多想多学多问，问题总会解决的