题目集4~6的总结
题目集四 7-2
代码：
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int choice= in.nextInt();
int year,month,day;
switch (choice){
case 1:
year = Integer.parseInt(in.next());
month = Integer.parseInt(in.next());
day = Integer.parseInt(in.next());
DateUtil date = new DateUtil(year, month, day);
if (!date.checkInputValidity()) {
System.out.print("Wrong Format");
System.exit(0);
}
int m = in.nextInt();
if (m < 0) {
System.out.print("Wrong Format");
System.exit(0);
}
System.out.print(date.getNextNDays(m).showDate());
break;
case 2:
year = Integer.parseInt(in.next());
month = Integer.parseInt(in.next());
day = Integer.parseInt(in.next());
DateUtil data = new DateUtil(year, month, day);
if (!data.checkInputValidity()) {
System.out.print("Wrong Format");
System.exit(0);
}
int n = in.nextInt();
if (n < 0) {
System.out.print("Wrong Format");
System.exit(0);
}
System.out.print(data.getPreviousNDays(n).showDate());
break;
case 3:
year = Integer.parseInt(in.next());
month = Integer.parseInt(in.next());
day = Integer.parseInt(in.next());
int anotherYear = Integer.parseInt(in.next());
int anotherMonth = Integer.parseInt(in.next());
int anotherDay = Integer.parseInt(in.next());
DateUtil fromDate = new DateUtil(year, month, day);
DateUtil toDate = new DateUtil(anotherYear, anotherMonth, anotherDay);
if (fromDate.checkInputValidity() && toDate.checkInputValidity()) {
System.out.print(fromDate.getDaysofDates(toDate));
} else {
System.out.print("Wrong Format");
System.exit(0);
}
break;
default:
System.out.print("Wrong Format");
System.exit(0);
break;
}
}
}
class DateUtil {
Day day;
public DateUtil() {
}
public DateUtil(int d, int m, int y) {
this.day = new Day(d, m, y);
}
public Day getDay() {
return day;
}
public void setDay(Day d) {
this.day = d;
}
public boolean checkInputValidity() {//检测输入的年、月、日是否合法
if (this.getDay().getMonth().getYear().validate() && this.getDay().getMonth().validate() && day.validate())
return true;
return false;
}
public boolean compareDates(DateUtil date) {//比较当前日期与date的大小（先后）
if (date.getDay().getMonth().getYear().getValue() < this.getDay().getMonth().getYear().getValue())
return false;
else if (date.getDay().getMonth().getYear().getValue() == this.getDay().getMonth().getYear().getValue()
&& date.getDay().getMonth().getValue() < this.getDay().getMonth().getValue())
return false;
if (date.getDay().getMonth().getYear().getValue() == this.getDay().getMonth().getYear().getValue()
&& date.getDay().getMonth().getValue() == this.getDay().getMonth().getValue()
&& date.getDay().getValue() < this.getDay().getValue())
return false;
return true;
}
public boolean equalTwoDates(DateUtil date) {//判断两个日期是否相等
if (this.getDay().getValue() == date.getDay().getValue()
&& this.getDay().getMonth().getYear().getValue() == date.getDay().getMonth().getYear().getValue()
&& this.getDay().getMonth().getValue() == date.getDay().getMonth().getValue())
return true;
return false;
}
public String showDate() {//以“year-month-day”格式返回日期值
return this.getDay().getMonth().getYear().getValue() + "-" + this.getDay().getMonth().getValue() + "-" + this.getDay().getValue();
}
public DateUtil getNextNDays(int n) {//取得year-month-day的下n天日期
int[] arr = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int year, month, day;
int rest = restday(this);
if (rest > n) {//本年
year = this.getDay().getMonth().getYear().getValue();
int Mday = arr[this.getDay().getMonth().getValue()];
if (this.getDay().getMonth().getYear().isLeapYear() && this.getDay().getMonth().getValue() == 2) {
Mday++;
}
Mday -= this.getDay().getValue();//本月剩余的日期
if (Mday >= n) { //本月
month = this.getDay().getMonth().getValue();
day = n + this.getDay().getValue();
} else { //其他月
n -= Mday;
month = this.getDay().getMonth().getValue() + 1;
int k = month;
while (n - arr[k] > 0) {
n -= arr[k];
month++;
k++;
}
day = n;
}
} else {
n -= rest;
year = this.getDay().getMonth().getYear().getValue() + 1;
int y = 365;
if (new Year(year).isLeapYear()) {
y++;
}
while (n - y > 0) {
n -= y;
year++;
y = 365;
if (new Year(year).isLeapYear())
y++;
}
int k = 1;
while (n - arr[k] > 0) {
n -= arr[k];
k++;
}
month = k;
day = n;
}
return new DateUtil(year, month, day);
}
public int restday(DateUtil d) {
int n = 0;
int[] arr = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
for (int i = d.getDay().getMonth().getValue() + 1; i <= 12; i++) {
n += arr[i];
}
n += arr[d.getDay().getMonth().getValue()] - d.getDay().getValue();
if (d.getDay().getMonth().getYear().isLeapYear() && d.getDay().getMonth().getValue() <= 2)
n++;
return n;
}
public DateUtil getPreviousNDays(int n) {//取得year-month-day的前n天日期
int[] arr = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int year, month, day;
int rest = 365 - restday(this);
if (this.getDay().getMonth().getYear().isLeapYear()) {
rest++;
}
if (rest > n) {//本年
year = this.getDay().getMonth().getYear().getValue();
int mday = this.getDay().getValue();//本月剩余的日期
if (mday > n) { //本月
month = this.getDay().getMonth().getValue();
day = mday - n;
} else { //其他月
n -= mday;
month = this.getDay().getMonth().getValue() - 1;
if (month == 0) {
month = 12;
year = this.getDay().getMonth().getYear().getValue() - 1;
}
int k = month;
while (n - arr[k] > 0) {
n -= arr[k];
month--;
k--;
}
day = arr[k] - n;
if (new Year(year).isLeapYear() && month == 2) {
day++;
}
}
} else {
n -= rest;
year = this.getDay().getMonth().getYear().getValue() - 1;
int y = 365;
if (new Year(year).isLeapYear()) {
y++;
}
while (n - y > 0) {
n -= y;
year--;
y = 365;
if (new Year(year).isLeapYear())
y++;
}
int k = 12;
while (n - arr[k] > 0) {
n -= arr[k];
k--;
}
month = k;
day = arr[k] - n;
if (new Year(year).isLeapYear() && month == 2) {
day++;
}
}
return new DateUtil(year, month, day);
}
public int getDaysofDates(DateUtil date) {//求当前日期与date之间相差的天数
DateUtil pred = this;
DateUtil nextd = date;
if (this.equalTwoDates(date)) {
return 0;
} else if (!this.compareDates(date)) {
pred = date;
nextd = this;
}
int[] arr = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int i, j, d = 0;
for (i = pred.getDay().getMonth().getYear().getValue() + 1; i < nextd.getDay().getMonth().getYear().getValue(); i++) {
d = d + 365;
if (new Year(i).isLeapYear())
d++;
}
if (pred.getDay().getMonth().getYear().getValue() != nextd.getDay().getMonth().getYear().getValue()) {
for (j = pred.getDay().getMonth().getValue() + 1; j <= 12; j++)
d = d + arr[j];
d += arr[pred.getDay().getMonth().getValue()] - pred.getDay().getValue();
for (j = 1; j < nextd.getDay().getMonth().getValue(); j++)
d += arr[j];
d += nextd.getDay().getValue();
if (pred.getDay().getMonth().getYear().isLeapYear() && pred.getDay().getMonth().getValue() <= 2)
d++;
if (nextd.getDay().getMonth().getYear().isLeapYear() && nextd.getDay().getMonth().getValue() > 2) {
d++;
}
} else if (pred.getDay().getMonth().getYear().getValue() == nextd.getDay().getMonth().getYear().getValue() && pred.getDay().getMonth().getValue() != nextd.getDay().getMonth().getValue()) {
for (j = pred.getDay().getMonth().getValue() + 1; j <= nextd.getDay().getMonth().getValue() - 1; j++)
d += arr[j];
d += arr[pred.getDay().getMonth().getValue()] - pred.getDay().getValue();
d += nextd.getDay().getValue();
if (pred.getDay().getMonth().getYear().isLeapYear() && pred.getDay().getMonth().getValue() <= 2)
d++;
} else if (pred.getDay().getMonth().getYear().getValue() == nextd.getDay().getMonth().getYear().getValue() && pred.getDay().getMonth().getValue() == nextd.getDay().getMonth().getValue()) {
d = nextd.getDay().getValue() - pred.getDay().getValue();
}
return d;
}
}
class Day{
int value;
Month month;
int[] mon_maxnum ={31,28,31,30,31,30,31,31,30,31,30,31};
public Day() {
}
public Day(int yearValue,int monthValue,int dayValue) {
this.month = new Month(yearValue,monthValue);
this.value = dayValue;
}
public int getValue() {
return value;
}
public void setValue(int value) {
this.value = value;
}
public Month getMonth() {
return month;
}
public void setMonth(Month value) {
this.month = value;
}
public void resetMin() {
value=1;
}
public void resetMax() {
value=mon_maxnum[month.getValue()-1];
}
public boolean validate() {
if(this.getMonth().getYear().isLeapYear())
mon_maxnum[1]++;
if(value>=1 && mon_maxnum[month.getValue()-1]>=value)
return true;
return false;
}
public void dayIncrement() {
value++;
}
public void dayReduction() {
value--;
}
}
class Month{
int value;
Year year;
public Month() {
}
public Month(int yearValue,int monthValue) {
this.year = new Year(yearValue);
this.value = monthValue;
}
public int getValue() {
return value;
}
public void setValue(int value) {
this.value = value;
}
public Year getYear() {
return year;
}
public void setYear(Year year) {
this.year = year;
}
public void resetMin() {
value=1;
}
public void resetMax() {
value=12;
}
public boolean validate() {
if(value>=1 && value<=12)
return true;
return false;
}
public void monthIncrement() {
value++;
}
public void monthReduction() {
value--;
}
}
class Year{
int value;
public Year() {
}
public Year(int value) {
this.value = value;
}
public int getValue() {
return value;
}
public void setValue(int value) {
this.value = value;
}
public boolean isLeapYear(){//判断year是否为闰年
boolean result;
result=(value%4 == 0 && value%100 != 0)||value%400 == 0;
if(result)
return true;
else
return false;
}
public boolean validate() {
if(value>=1900 && value<=2050)
return true;
return false;
}
public void yearIncrement() {
value++;
}
public void yearReduction() {
value--;
}
}
题目集五7-5
代码：
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int choice= in.nextInt();
int year,month,day;
switch (choice){
case 1:
year = Integer.parseInt(in.next());
month = Integer.parseInt(in.next());
day = Integer.parseInt(in.next());
DateUtil date = new DateUtil(year, month, day);
if (!date.checkInputValidity()) {
System.out.print("Wrong Format");
System.exit(0);
}
int m = in.nextInt();
if (m < 0) {
System.out.print("Wrong Format");
System.exit(0);
}
System.out.print(date.showDate() + " next " + m + " days is:"+date.getNextNDays(m).showDate());
break;
case 2:
year = Integer.parseInt(in.next());
month = Integer.parseInt(in.next());
day = Integer.parseInt(in.next());
DateUtil data = new DateUtil(year, month, day);
if (!data.checkInputValidity()) {
System.out.print("Wrong Format");
System.exit(0);
}
int n = in.nextInt();
if (n < 0) {
System.out.print("Wrong Format");
System.exit(0);
}
System.out.print(data.showDate() + " previous " + n + " days is:"+data.getPreviousNDays(n).showDate());
break;
case 3:
year = Integer.parseInt(in.next());
month = Integer.parseInt(in.next());
day = Integer.parseInt(in.next());
int anotherYear = Integer.parseInt(in.next());
int anotherMonth = Integer.parseInt(in.next());
int anotherDay = Integer.parseInt(in.next());
DateUtil fromDate = new DateUtil(year, month, day);
DateUtil toDate = new DateUtil(anotherYear, anotherMonth, anotherDay);
if (fromDate.checkInputValidity() && toDate.checkInputValidity()) {
System.out.print("The days between " + fromDate.showDate() + " and " + toDate.showDate() + " are:"
+ fromDate.getDaysofDates(toDate));
} else {
System.out.print("Wrong Format");
System.exit(0);
}
break;
default:
System.out.print("Wrong Format");
System.exit(0);
break;
}
}
}
class DateUtil {
Year year;
Month month;
Day day;
int[] mon_maxnum ={31,28,31,30,31,30,31,31,30,31,30,31};
public DateUtil() {
}
public DateUtil(int y, int m, int d) {
this.day = new Day(d);
this.month = new Month(m);
this.year = new Year(y);
}
public Year getYear(){
return year;
}
public void setYear(Year year){
this.year=year;
}
public Month getMonth(){
return month;
}
public void setMonth(Month month){
this.month=month;
}
public Day getDay() {
return day;
}
public void setDay(Day day) {
this.day = day;
}
public void setDayMin(){
this.day.value=1;
}
public void getDayMax(){
if(this.year.isLeapYear())
mon_maxnum[1]++;
this.day.value=mon_maxnum[this.month.value-1];
}
public boolean checkInputValidity() {//检测输入的年、月、日是否合法
if (this.getYear().validate() && this.getMonth().validate()){
if(!new Year(this.getYear().getValue()).isLeapYear()){
if(this.getDay().getValue()<=mon_maxnum[this.getMonth().getValue()-1])
return true;
}
else if(this.getDay().getValue()<=mon_maxnum[this.getMonth().getValue()-1] || this.getDay().getValue()==29)
return true;
}
return false;
}
public DateUtil getNextNDays(int n) {//取得year-month-day的下n天日期
int[] arr = {0,31,28,31,30,31,30,31,31,30,31,30,31};
int year, month, day;
int rest = restday(this);
if (rest>n) {//本年
year=this.getYear().getValue();
int mday = arr[this.getMonth().getValue()];
if (this.getYear().isLeapYear()&&this.getMonth().getValue()==2) {
mday++;
}
mday-=this.getDay().getValue();//本月剩余的日期
if (mday>=n) { //本月
month = this.getMonth().getValue();
day = n+this.getDay().getValue();
}
else{ //其他月
n-=mday;
month = this.getMonth().getValue()+1;
int k = month;
while(n-arr[k]>0){
n -= arr[k];
month++;
k++;
}
day = n;
}
}
else {
n-=rest;
year = this.getYear().getValue()+1;
int y = 365;
if (new Year(year).isLeapYear()) {
y++;
}
while(n-y>0){
n-=y;
year++;
y=365;
if (new Year(year).isLeapYear())
y++;
}
int k = 1;
while(n-arr[k]>0){
n -= arr[k];
k++;
}
month = k;
day = n;
}
return new DateUtil(year, month, day);
}
public DateUtil getPreviousNDays(int n) {//取得year-month-day的前n天日期
int arr[] = {0,31,28,31,30,31,30,31,31,30,31,30,31};
int year, month, day;
int rest = 365-restday(this);
if (this.getYear().isLeapYear()) {
rest++;
}
if (rest>n) {//本年
year=this.getYear().getValue();
int mday=this.getDay().getValue();//本月剩余的日期
if (mday>n) { //本月
month = this.getMonth().getValue();
day = mday-n;
}
else{ //其他月
n-=mday;
month = this.getMonth().getValue()-1;
if (month==0) {
month = 12;
year=this.getYear().getValue()-1;
}
int k = month;
while(n-arr[k]>0){
n -= arr[k];
month--;
k--;
}
day = arr[k]-n;
if (new Year(year).isLeapYear()&&month==2) {
day++;
}
}
}
else {
n-=rest;
year = this.getYear().getValue()-1;
int y = 365;
if (new Year(year).isLeapYear()) {
y++;
}
while(n-y>0){
n-=y;
year--;
y=365;
if (new Year(year).isLeapYear())
y++;
}
int k = 12;
while(n-arr[k]>0){
n -= arr[k];
k--;
}
month = k;
day = arr[k]-n;
if (new Year(year).isLeapYear()&&month==2) {
day++;
}
}
return new DateUtil(year, month, day);
}
public boolean compareDates(DateUtil date) {//比较当前日期与date的大小（先后）
if (date.getYear().getValue() < this.getYear().getValue())
return false;
else if (date.getYear().getValue() == this.getYear().getValue()
&& date.getMonth().getValue() < this.getMonth().getValue())
return false;
if (date.getYear().getValue() == this.getYear().getValue()
&& date.getMonth().getValue() == this.getMonth().getValue()
&& date.getDay().getValue() < this.getDay().getValue())
return false;
return true;
}
public int restday(DateUtil d) {
int n = 0;
int arr[] = {0,31,28,31,30,31,30,31,31,30,31,30,31};
for (int i = d.getMonth().getValue()+1; i <=12; i++) {
n+=arr[i];
}
n+=arr[d.getMonth().getValue()]-d.getDay().getValue();
if(d.getYear().isLeapYear()&&d.getMonth().getValue()<=2)
n++;
return n;
}
public boolean equalTwoDates(DateUtil date) {//判断两个日期是否相等
if (this.getDay().getValue() == date.getDay().getValue()
&& this.getMonth().getValue() == date.getMonth().getValue()
&& this.getYear().getValue() == date.getYear().getValue())
return true;
return false;
}
public int getDaysofDates(DateUtil date) {//求当前日期与date之间相差的天数
DateUtil pred = this;
DateUtil nextd = date;
if (this.equalTwoDates(date)) {
return 0;
} else if (!this.compareDates(date)){
pred = date;
nextd = this;
}
int[] arr = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int i, d = 0;
for (i = pred.getYear().getValue() + 1; i < nextd.getYear().getValue(); i++) {
d = d + 365;
if (new Year(i).isLeapYear())
d++;
}
for(i=pred.getMonth().getValue()+1;i<=12;i++){
if(i==2 && new Year(pred.getYear().getValue()).isLeapYear())
d++;
d+=arr[i];
}
d+=arr[pred.getMonth().getValue()]-pred.getDay().getValue();
for(i=1;i<nextd.getMonth().getValue();i++){
d+=arr[i];
}
if(new Year(nextd.getYear().getValue()).isLeapYear() && (nextd.getMonth().getValue()>2 || nextd.getDay().getValue()==29))
d++;
d+=nextd.getDay().getValue();
return d;
}
public String showDate() {//以“year-month-day”格式返回日期值
return this.getYear().getValue() + "-" + this.getMonth().getValue() + "-" + this.getDay().getValue();
}
}
class Day{
int value;
public Day() {
}
public Day(int value) {
this.value =value;
}
public int getValue() {
return value;
}
public void setValue(int value) {
this.value = value;
}
public void dayIncrement() {
value++;
}
public void dayReduction() {
value--;
}
}
class Month{
int value;
public Month() {
}
public Month(int value) {
this.value =value;
}
public int getValue() {
return value;
}
public void setValue(int value) {
this.value = value;
}
public void resetMin() {
value=1;
}
public void resetMax() {
value=12;
}
public boolean validate() {
if(value>=1 && value<=12)
return true;
return false;
}
public void monthIncrement() {
value++;
}
public void monthReduction() {
value--;
}
}
class Year{
int value;
public Year() {
}
public Year(int value) {
this.value = value;
}
public int getValue() {
return value;
}
public void setValue(int value) {
this.value = value;
}
public boolean isLeapYear(){//判断year是否为闰年
boolean result;
result=(value%4 == 0 && value%100 != 0)||value%400 == 0;
if(result)
return true;
else
return false;
}
public boolean validate() {
if(value>=1820 && value<=2020)
return true;
return false;
}
public void yearIncrement() {
value++;
}
public void yearReduction() {
value--;
}
}
比较：
题目集四7-2类图
题目集五7-5类图：
比较：可以看出，这两题几乎一模一样，但在构建类的思想上有所不同，第一种采用分开年月日，层层依赖，牵一发而动全身，而第二种就有所不同了，在一个类DateUtil里囊括年月日的调用思想，如果后续要加入其他功能的话，第二种应该是要比第一种更适合编辑修改。
题目集四 7-3
代码：
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
int choice=in.nextInt();
switch (choice){
case 1 :{
double r = in.nextDouble();
if (r <= 0){
System.out.print("Wrong Format");
System.exit(-1);//输入错误，直接结束；
}
Circle circle = new Circle();
circle.setRadius(r);
System.out.printf("Circle's area:%.2f",circle.getArea());
break;
}
case 2 :{
double length = in.nextDouble();
double width = in.nextDouble();
if (length <= 0 || width <= 0){
System.out.print("Wrong Format");
System.exit(-1);
}
Rectangle rectangle = new Rectangle();
rectangle.setLength(length);
rectangle.setWidth(width);
System.out.printf("Rectangle's area:%.2f",rectangle.getArea());
break;
}
case 3 :{
double radius = in.nextDouble();
if (radius <= 0){
System.out.print("Wrong Format");
System.exit(-1);
}
Ball ball = new Ball();
ball.setRadius(radius);
System.out.printf("Ball's surface area:%.2f\n",ball.getArea());
System.out.printf("Ball's volume:%.2f",ball.getVolume());
break;
}
case 4 :{
double length = in.nextDouble();
double width = in.nextDouble();
double height = in.nextDouble();
if (length <= 0 || width <= 0 || height <= 0){
System.out.print("Wrong Format");
System.exit(-1);
}
Box box = new Box();
box.setLength(length);
box.setWidth(width);
box.setHeight(height);
System.out.printf("Box's surface area:%.2f\n",box.getArea());
System.out.printf("Box's volume:%.2f",box.getVolume());
break;
}
default :
System.out.print("Wrong Format");
System.exit(-1);
}
}
}
class Shape{
public Shape(){
System.out.println("Constructing Shape");
}
public double getArea(){
return 0.0;
}
}
class Circle extends Shape{//求圆面积
private double radius;
public Circle(){
System.out.println("Constructing Circle");
}
public double getRadius(){
return radius;
}
public void setRadius(double radius){
this.radius = radius;
}
public double getArea(){
return Math.pow(radius,2)* Math.PI;
}
}
class Rectangle extends Shape{//求矩形面积
private double width;
private double length;
public Rectangle(){
System.out.println("Constructing Rectangle");
}
public double getWidth(){
return width;
}
public void setWidth(double width){
this.width = width;
}
public double getLength(){
return length;
}
public void setLength(double length) {
this.length = length;
}
public double getArea(){
return width * length;
}
}
class Ball extends Circle{//求球的表面积和体积
public Ball(){
System.out.println("Constructing Ball");
}
public double getArea(){
return 4 * Math.pow(super.getRadius(),2) * Math.PI;
}
public double getVolume(){
return 4.0 / 3.0 * Math.PI * Math.pow(super.getRadius(), 3);
}
}
class Box extends Rectangle{//求立方体的表面积和体积
private double height;
public Box(){
System.out.println("Constructing Box");
}
public double getHeight(){
return height;
}
public void setHeight(double height){
this.height = height;
}
public double getArea(){
return (super.getArea() + height * super.getWidth() + height * super.getLength()) * 2;
}
public double getVolume(){
return height * super.getArea();
}
}
分析：这是典型的继承题目，球继承了圆形的各项属性和方法，立方体继承了矩形的各项属性和方法，这种继承的好处在于，在实现想要获取的图形不同时，比如圆和球体都需要，采用继承，可以分别获取，也避免了球体重复圆形的方法，减少了冗余度，整个代码工整。
题目集六 7-5
代码：
import java.util.Scanner;
import java.util.Arrays;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int a=in.nextInt();
int b=in.nextInt();
int c=in.nextInt();
if (a<0 || b<0 ||c<0){
System.out.print("Wrong Format");
System.exit(-1);
}
double[] A=new double[a+b+c];
int j=0;
for(int i=0;i<a;i++){
double radius=in.nextDouble();
if (radius <= 0){
System.out.print("Wrong Format");
System.exit(-1);//输入错误，直接结束；
}
Circle circle = new Circle();
circle.setRadius(radius);
A[j]=circle.getArea();
j++;
}
for(int i=0;i<b;i++){
double width=in.nextDouble();
double length=in.nextDouble();
if (length <= 0 || width <= 0){
System.out.print("Wrong Format");
System.exit(-1);
}
Rectangle rectangle = new Rectangle();
rectangle.setLength(length);
rectangle.setWidth(width);
A[j]=rectangle.getArea();
j++;
}
for(int i=0;i<c;i++){
double side1=in.nextDouble();
double side2=in.nextDouble();
double side3=in.nextDouble();
if (side1+side2<=side3 ||side1+side3<=side2 || side2+side3<=side1 || side1<=0 || side2<=0 || side3<=0){
System.out.print("Wrong Format");
System.exit(-1);
}
Triangle triangle= new Triangle();
triangle.setSide1(side1);
triangle.setSide2(side2);
triangle.setSide3(side3);
A[j]=triangle.getArea();
j++;
}
System.out.println("Original area:");
double sum=0;
for(int k=0;k<a+b+c;k++){
System.out.printf("%.2f ",A[k]);
sum+=A[k];
}
System.out.print("\n");
System.out.printf("Sum of area:%.2f\n",sum);
Arrays.sort(A);
System.out.println("Sorted area:");
for(int k=0;k<a+b+c;k++){
System.out.printf("%.2f ",A[k]);
}
System.out.print("\n");
System.out.printf("Sum of area:%.2f",sum);
}
}
class Shape{
public double getArea(){
return 0.0;
}
}
class Circle extends Shape{//求圆面积
private double radius;
public double getRadius(){
return radius;
}
public void setRadius(double radius){
this.radius = radius;
}
public boolean validate(double radius){
return radius>0;
}
public double getArea(){
return Math.pow(radius,2)* Math.PI;
}
}
class Rectangle extends Shape{//求矩形面积
private double width;
private double length;
public double getWidth(){
return width;
}
public void setWidth(double width){
this.width = width;
}
public double getLength(){
return length;
}
public void setLength(double length) {
this.length = length;
}
public double getArea(){
return width * length;
}
}
class Triangle extends Shape{//求三角形面积
private double side1;
private double side2;
private double side3;
public double getSide1(){
return side1;
}
public void setSide1(double side1) {
this.side1 = side1;
}
public double getSide2(){
return side2;
}
public void setSide2(double side2) {
this.side2 = side2;
}
public double getSide3(){
return side3;
}
public void setSide3(double side3) {
this.side3 = side3;
}
public boolean validate(double side1,double side2,double side3){
return side1+side2>side3;
}
public double getArea(){
return (1.0/4.0)*Math.sqrt((side1+side2+side3)*(side1+side2-side3)*(side1+side3-side2)*(side2+side3-side1));
}
}
分析:这题和上题一样，用到的继承方法如出一辙，不同的只是在主函数调用的地方用了一些循环，在中心思想上差不多。
题目集六7-6
代码：
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
double radius=in.nextDouble();
double width=in.nextDouble();
double length=in.nextDouble();
if (radius <= 0){
System.out.print("Wrong Format");
System.exit(-1);//输入错误，直接结束；
}
Circle circle = new Circle();
circle.setRadius(radius);
if (length <= 0 || width <= 0){
System.out.print("Wrong Format");
System.exit(-1);
}
Rectangle rectangle = new Rectangle();
rectangle.setLength(length);
rectangle.setWidth(width);
System.out.printf("%.2f\n",circle.getArea());
System.out.printf("%.2f",rectangle.getArea());
}
}
class Shape{
public double getArea(){
return 0.0;
}
}
class Circle extends Shape{//求圆面积
private double radius;
public double getRadius(){
return radius;
}
public void setRadius(double radius){
this.radius = radius;
}
public boolean validate(double radius){
return radius>0;
}
public double getArea(){
return Math.pow(radius,2)* Math.PI;
}
}
class Rectangle extends Shape{//求矩形面积
private double width;
private double length;
public double getWidth(){
return width;
}
public void setWidth(double width){
this.width = width;
}
public double getLength(){
return length;
}
public void setLength(double length) {
this.length = length;
}
public double getArea(){
return width * length;
}
}
class Triangle extends Shape{//求三角形面积
private double side1;
private double side2;
private double side3;
public double getSide1(){
return side1;
}
public void setSide1(double side1) {
this.side1 = side1;
}
public double getSide2(){
return side2;
}
public void setSide2(double side2) {
this.side2 = side2;
}
public double getSide3(){
return side3;
}
public void setSide3(double side3) {
this.side3 = side3;
}
public boolean validate(double side1,double side2,double side3){
return side1+side2>side3;
}
public double getArea(){
return (1.0/4.0)*Math.sqrt((side1+side2+side3)*(side1+side2-side3)*(side1+side3-side2)*(side2+side3-side1));
}
}
分析:这题也是一样的继承，不过少了三角形的类，每个图形继承自形状的特点。
题目集五 7-4
代码：
import java.util.*;
import java.util.regex.*;
public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
String important="abstract assert boolean break byte case catch char class const continue default do " +
" double else enum extends final finally float for goto if implements import instanceof int " +
"interface long native new package private protected public return strictfp short static super " +
"switch synchronized this throw throws transient try void volatile while true false null";
String []end=important.split(" ");
Map<String,Integer> mp= new TreeMap<>();
for(String e:end) mp.put(e,0);
String s;
int flag=0;
StringBuilder t=new StringBuilder();
while(!(s=in.nextLine().trim()).equals("exit")){
if(s.matches(".*//.*")) continue;
t.append(s).append(" ");
}
s=t.toString();
s=change(s);
Pattern p=Pattern.compile("/\\*(.*)?\\*/");
Matcher m=p.matcher(s);
while(m.find()){
s=s.replace(m.group()," ");
m=p.matcher(s);
}
p=Pattern.compile("\"(.*?)\"");
m=p.matcher(s);
while(m.find()){
s=s.replace(m.group()," ");
m=p.matcher(s);
}
if(s.length()==0){ System.out.print("Wrong Format");System.exit(0);}
s=s.replaceAll("\\p{P}"," ");
String[] temp=s.split("\\s+");
for(String e:temp)
if(mp.containsKey(e)) { mp.put(e,mp.get(e)+1);flag=1; }
if(flag==0) System.exit(0);
List<Map.Entry<String, Integer>> list= new ArrayList<>(mp.entrySet());
list.stream().sorted(Map.Entry.comparingByKey()).filter(u-> u.getValue()!=0).forEach(u-> System.out.printf("%d\t%s\n",u.getValue(),u.getKey()));
}
static String []special = {"\\$","_","int\\(\\)","boolean\\(\\)","double\\(\\)","float\\(\\)","byte\\(\\)","long\\(\\)","short\\(\\)","\\*"};
public static String change(String s){
if (s.length()<800) return s;
for (String e: special) s = s.replaceAll(e, "CYQ");
return s;
}
}
分析：这道题先用正则表达式处理输入的字符串，然后模式匹配java关键字，表面处理起来没啥问题，但是细究会发现没那么简单，题目测试点有很多没发现的地方，让我一头雾水，最后在同学的帮助下完成了这道题，总的来说，这道题还是很有借鉴思路的。
总结:这三次作业集，明显地可以看出难度上来了，也意味着我们向着更高深的java知识迈进，学到了很多，这次的作业分析，希望能够帮助了大家。
