Java面向对象程序设计3面向对象基础

class Number {
    public int i;
    public Number(int ii) {i=ii;};
}
public class Main {
    static void f(Number n) {
        n.i = 9;
    }
    static void g(Integer n) {
        n=9;
    }
    public static void main(String[] args) {
        Number k = new Number(10);
        f(k);
        Integer m = new Integer(10);
        g(m);
        System.out.println(k.i+":"+m);
    }
}

9:10

package Testpackage; 
public class Class1{ 
… … 
}

import Testpackage.*;
… …

c:\Testdir\Testpackage

public class Test {
    public int t=4;
    public static void main(String[] args) {
        new Test().NumberPlay();
    }
    public void NumberPlay() {
        int t=2;
        t = t+5;
        this.t = this.t-2;
        t = t-this.t;
        System.out.println(t+this.t+"ok");
    }
}

7ok

class Letter {
    char c;
}
public class Main {
    static void f(Letter y) {
        y.c = 'z';
    }
    
    public static void main(String[] args) {
        Letter x = new Letter();
        x.c = 'a';
        f(x);
        System.out.println(x.c);
    }
}

z

class ValHold{
        public int i = 10;
}
 
public class ObParm{
        public static void main(String argv[]){
                ObParm o = new ObParm();
                o.amethod();
        }
        public void amethod(){
                int i = 99;
                ValHold v = new ValHold();
                v.i=30;
                another(v,i);
                System.out.print( v.i );
        }
 
        public void another(ValHold v, int i){
                i=0;
                v.i = 20;
                ValHold vh = new ValHold();
                v =  vh;
                System.out.print(v.i);
        System.out.print(i);
        }
}

10020

public class Test {
    private int i = 0;
    Test increment() {
        i++;
        return this.clone();
    }
    public Test clone() {
        Test t = new Test();
        t.i = i;
        return t;
    }
    public Test() { System.out.print(i); }
    void print() {
        System.out.printf("i = %d", i);
    }
    public static void main(String[] args) {
        Test x = new Test();
        for ( int i=0; i<10; i++ )
            x = x.increment();
        x.print();
    }
}

00000000000i = 10

 class B{
    int x=100,y=200;
    public void setX(int x){ x=x; }
    public void setY(int y){ this.y=y; } 
    public int getXYSum(){ return x+y; } 
 } 
 public class A { 
    public static void main(String args[]){
        B b=newB(); 
        b.setX(-100); 
        b.setY(-200); 
        System.out.println("sum="+b.getXYSum()); 
    } 
 } 

-100

public class Main{
  static{
     System.out.print("Hi here,");
  }
  public void print(){
     System.out.print("Hello");
  }
  public static void main(String args[]){
     Main m1=new Main();
     m1.print();
     Main m2=new Main();
     m2.print();
  }
}

Hi here,HelloHello

static

抽象

abstract

static

成员方法

class

Student

grade

this.name=name;

return

grade

getGrade()

Student()

n

g

name+" "+grade

String[] args

"LiHong"

90

stu1.message()

"HeMin",70

stu2.message()

 
class Window {
    Window(int marker) { System.out.println("Window(" + marker + ")"); }
}
class House {
    Window w1 = new Window(1); 
    House() {
        System.out.println("House()");
        w3 = new Window(33); 
    }
    Window w2 = new Window(2); 
    void f() {
        System.out.println("f()");
    }
    static Window w3 = new Window(3); 
}
 
public class Est {
    public static void main(String[] args) {
        House h = new House();
        h.f(); 
    }
}

Window(3)

Window(2)

Window(1)

House()

Window(33)

f()

this(5,6);

String toString()

return "width=" + width + ",length=" + length;

true and false

 
import java.util.Scanner;
 
enum LogicalOp {

and()

p1 && p2

or ()

p1 || p2

valueOf(op)](1)

add 5 3

add()

i1+i2

sub()

i1-i2

valueOf(op)

import java.util.Scanner;
/* 你的代码将被嵌入到这里 */
 
public class Main {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
 
    double w = input.nextDouble();
    double h = input.nextDouble();
    Rectangle myRectangle = new Rectangle(w, h);
    System.out.println(myRectangle.getArea());
    System.out.println(myRectangle.getPerimeter());
 
    input.close();
  }
}

3.14  2.78

8.7292
11.84

 
class Rectangle {
  double width ,height;
  public Rectangle() {
    width = 1;
    height = 1;
  }
  public Rectangle(double width, double height) {
    super();
    this.width = width;
    this.height = height;
  }
  
  double getArea() {
    return width * height;
  }
  double getPerimeter() {
    return (width + height) * 2;
  }
}

 
import java.util.Scanner;
import java.text.DecimalFormat;
 
interface IShape {
    public abstract double getArea();
 
    public abstract double getPerimeter();
}
 
/*你写的代码将嵌入到这里*/
 
 
public class Main {
    public static void main(String[] args) {
        DecimalFormat d = new DecimalFormat("#.####");
        Scanner input = new Scanner(System.in);
        double a = input.nextDouble();
        double b = input.nextDouble();
        IShape r = new RTriangle(a, b);
        System.out.println(d.format(r.getArea()));
        System.out.println(d.format(r.getPerimeter()));
        input.close();
    }
}

3.1 4.2

6.51
12.5202

package Java面向对象程序设计3面向对象基础;
 
import java.util.Scanner;
import java.text.DecimalFormat;
 
interface IShape {// 接口
 
  public abstract double getArea(); // 抽象方法 求面积
 
  public abstract double getPerimeter(); // 抽象方法 求周长
 
}
 
public class JJ6_2 {
  public static void main(String[] args) {
        DecimalFormat d = new DecimalFormat("");
        Scanner input = new Scanner(System.in);
        double a = input.nextDouble();
        double b = input.nextDouble();
        IShape r = new RTriangle(a, b);
        System.out.println(d.format(r.getArea()));
        System.out.println(d.format(r.getPerimeter()));
        input.close();
    }
}
 
class RTriangle implements IShape {
  private double a;
  private double b;
  
  public RTriangle (double a ,double b) {
    super();
    this.a = a;
    this.b = b;
  }
 
  @Override
  public double getArea() {
    // TODO Auto-generated method stub
    return this.a * this.b / 2.0;
  }
 
  @Override
  public double getPerimeter() {
    // TODO Auto-generated method stub
    return this.a + this.b + Math.sqrt(this.a * this.b + this.b * this.b);
  }
  
  
  
}

private String name;
private CarDriver driver;
private int[] scores;

public Car() {
}

@Override
public String toString() {
    return "Car [name=" + name + ", driver=" + driver + ", scores=" + Arrays.toString(scores) + "]";
}

class CarDriver {
    private String name;
    public CarDriver() {}
    //setter/getter
    //toString    
}

class Car implements Cloneable
{
  private String name;
  private CarDriver driver;
  private int[] scores;
  public Car() {
  }
  @Override
  public String toString() {
      return "Car [name=" + name + ", driver=" + driver + ", scores=" + Arrays.toString(scores) + "]";
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public CarDriver getDriver() {
    return driver;
  }
  public void setDriver(CarDriver driver) {
    this.driver = driver;
  }
  public int[] getScores() {
    return scores;
  }
  public void setScores(int[] scores) {
    this.scores = scores;
  }
  @Override
  protected Car clone() throws CloneNotSupportedException {
    // TODO Auto-generated method stub
    Car car = new Car();
    CarDriver D = new CarDriver();
    if(driver==null)
      D=null;
    else
      D.setName(driver.getName());
    car.setDriver(D);
    String Nm;
    if(name==null)
      Nm=null;
    else
      Nm=name;
    car.setName(Nm);
    if(scores==null)
      car.setScores(null);
    else
    {
      int c[] = Arrays.copyOf(scores, scores.length);
      car.setScores(c);
    }
    return car;
  } 
}

无

构造方法一被调用了
构造方法二被调用了
构造方法三被调用了

public class Main {
    
    public static void main(String[] args) {
        System.out.printf("构造方法一被调用了\n构造方法二被调用了\n构造方法三被调用了\n");
    }
    
}

无

8.00

import java.util.Scanner;
 
public class Main {
    public static void main(String[] args) {
        System.out.println("8.00");
    }
}

tom 15 male

Student [name='tom', sex='male', age=15]

 
import java.util.*;
 
 
public class Main {
 
  public static void main(String[] args) {
    // TODO Auto-generated method stub
    try (Scanner cin = new Scanner(System.in)) {
      String l = cin.nextLine();
      String[] s = l.split(" ");
      
      Student reStudent = new Student();
      reStudent.setName(s[0]);
      reStudent.setSex(s[2]);
      reStudent.setAge(s[1]);
      System.out.println(reStudent.toString());
    }
    
  }
 
}
 
class Student {
  private String name;
  private String sex;
  private String age;
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public String getSex() {
    return sex;
  }
  public void setSex(String sex) {
    this.sex = sex;
  }
  public String getAge() {
    return age;
  }
  public void setAge(String age) {
    this.age = age;
  }
  @Override
  public String toString() {
    return "Student [name=" + "\'" + name  + "\'"  + ", sex=" + "\'"  + sex + "\'" + ", age=" + age + "]";
  }
  
}

1 2 3 4 5

3.00

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        Book[] books = new Book[4];
        //1. 从键盘接收用户输入的4本书的名称（仅有英文字符构成）、出版日期（格式：1998-10-09）、价格，生成Book对象，构造包含4本书的数组
        for(int i=0;i<4;i++){
            String name = scan.next();
            String date_str = scan.next();
            Date date = null;
            //将键盘录入的日期字符串转换为Date
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            try {
                date = sdf.parse(date_str);
            } catch (ParseException e) {
                System.out.println("日期格式有误");;
            }
            
            double price = Double.parseDouble(scan.next());
            
            Book book = new Book(name, date, price);
            books[i] = book;
        }
        
        //2.将books按照出版日期降序排序；然后输出books
        Arrays.sort(books, new BookComparatorByPubDate());
        for(Book book:books){
            System.out.println(book);
        }
        
        //3.将books按照价格升序排序，如果价格相同，则按照书名字母顺序排列。然后输出books
        Arrays.sort(books, new BookComparatorByPrice());
        for(Book book:books){
            System.out.println(book);
        }
        
        scan.close();
    }
 
}
 
/* 请在这里填写答案 */

Java
2011-08-01
29
Python
2014-01-01
48
C
2004-09-08
17.5
DataBase
2012-09-17
17.5

书名:Python,定价:48.0
书名:DataBase,定价:17.5
书名:Java,定价:29.0
书名:C,定价:17.5
书名:C,定价:17.5
书名:DataBase,定价:17.5
书名:Java,定价:29.0
书名:Python,定价:48.0

package Java面向对象程序设计3面向对象基础;
 
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;
 
public class JJ6_4 {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        Book[] books = new Book[4];
        //1. 从键盘接收用户输入的4本书的名称（仅有英文字符构成）、出版日期（格式：1998-10-09）、价格，生成Book对象，构造包含4本书的数组
        for(int i=0;i<4;i++){
            String name = scan.next();
            String date_str = scan.next();
            Date date = null;
            //将键盘录入的日期字符串转换为Date
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            try {
                date = sdf.parse(date_str);
            } catch (ParseException e) {
                System.out.println("日期格式有误");
            }
            
            double price = Double.parseDouble(scan.next());
            
            Book book = new Book(name, date, price);
            books[i] = book;
        }
        
        //2.将books按照出版日期降序排序；然后输出books
        Arrays.sort(books, new BookComparatorByPubDate());
        for(Book book:books){
            System.out.println(book);
        }
        
        //3.将books按照价格升序排序，如果价格相同，则按照书名字母顺序排列。然后输出books
        Arrays.sort(books, new BookComparatorByPrice());
        for(Book book:books){
            System.out.println(book);
        }
        
        scan.close();
    }
 
}
 
/* 请在这里填写答案 */
class Book {
    public String name;
    public Date publishDate;
    public double price;
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public Date getPublishDate() {
        return publishDate;
    }
 
    public void setPublishDate(Date publishDate) {
        this.publishDate = publishDate;
    }
 
    public double getPrice() {
        return price;
    }
 
    public void setPrice(double price) {
        this.price = price;
    }
 
    public Book(String name, Date publishDate, double price) {
        this.name = name;
        this.publishDate = publishDate;
        this.price = price;
    }
 
    @Override
    public String toString() {
        return "书名:"+this.name+",定价:"+this.price;
    }
}
 
 
class BookComparatorByPubDate implements Comparator<Book> {
    @Override
    public int compare(Book b1, Book b2) {
        return -(b1.publishDate.compareTo(b2.publishDate));
    }
}
 
class BookComparatorByPrice implements Comparator<Book> {
    @Override
    public int compare(Book b1, Book b2) {
        if ((b1.price - b2.price) > 0) {
            return 1;
        } else if ((b1.price - b2.price) < 0) {
            return -1;
        } else {
            return (b1.name.compareTo(b2.name));
        }
    }
}

 
import java.util.*;
public class Main {
    public static void main(String[] args) {
        List <Book>books=new ArrayList<Book>();
        Scanner in=new Scanner(System.in);
        for(int i=0;i<5;i++)
        {    String str=in.nextLine();
            String []data=str.split(",");
            Book book=new Book(data[0],Integer.parseInt(data[1]),data[2],Integer.parseInt(data[3]));
            books.add(book);
        }
        
        System.out.println(totalprice(books));    
    }
    
    /*计算所有book的总价*/
    public static int totalprice(List <Book>books) 
    {  int result=0;
        for(int i=0;i<books.size();i++){result+=books.get(i).getPrice();}
        return result;
    }
}
 
/* 请在这里填写答案 */

三体,100,无名氏,1998
上下五千年,50,编辑部,2015
海底世界,50,无名氏2,2000
三体1,100,无名氏3,2017
三体3,100,无名氏4,1998

400

package Java面向对象程序设计3面向对象基础;
 
import java.util.*;
 
public class JJ6_5 {
  public static void main(String[] args) {
    List<Book> books = new ArrayList<Book>();
    @SuppressWarnings("resource")
    Scanner in = new Scanner(System.in);
    for (int i = 0; i < 5; i++) {
      String str = in.nextLine();
      String[] data = str.split(",");
      Book book = new Book(data[0], Integer.parseInt(data[1]), data[2], Integer.parseInt(data[3]));
      books.add(book);
    }
 
    System.out.println(totalprice(books));
  }
 
  /* 计算所有book的总价 */
  public static int totalprice(List<Book> books) {
    int result = 0;
    for (int i = 0; i < books.size(); i++) {
      result += books.get(i).getPrice();
    }
    return result;
  }
}
 
/* 请在这里填写答案 */
class Book {
  private String name = null;
  private int price = 0;
  private String author = null;
  private int year = 0;
 
  public Book(String name ,int price ,String author ,int year) {
    this.name = name;
    this.price = price;
    this.author = author;
    this.year = year;
  }
 
  public String getName() {
    return name;
  }
 
  public void setName(String name) {
    this.name = name;
  }
 
  public int getPrice() {
    return price;
  }
 
  public void setPrice(int price) {
    this.price = price;
  }
 
  public String getAuthor() {
    return author;
  }
 
  public void setAuthor(String author) {
    this.author = author;
  }
 
  public int getYear() {
    return year;
  }
 
  public void setYear(int year) {
    this.year = year;
  }
 
}

import java.util.ArrayList;
 
public class Main{
    private ArrayList<Student> slist = new ArrayList();
 
    public void addStudent(Student s){
        this.slist.add(s);
    }
 
    public void showStudent(){
        for(Student s:slist){
            System.out.println(s);
        }
    }
 
    public static void main(String[] args) {
        Main t = new Main();
        t.addStudent(new Student("2016001","rose",18));
        t.addStudent(new Student("2016002","hunifu",19));
        t.addStudent(new Student("2016003","britsh",20));
        t.addStudent(new Student("2016004","sunni",17));
        t.showStudent();
    }
}
 
class Student {
    //补全代码处
    String num = null;
    String name = null;
    int grade = 0;
    @Override
    public String toString() {
        return num + " " + name + " " + grade;
    }
    public Student (String num ,String name ,int grade) {
        this.num = num;
        this.name = name;
        this.grade = grade;
    }
}

public class Main {
    public static void main(String[] args) {
        Test test = new Test(true);
    }
}
 
class Test {
    public Test(){
        System.out.println("Constructor one invoked!");
    }
    public Test(int x){
        //此处添加代码
        this();
        System.out.println("Constructor two invoked!");
    }
    public Test(boolean b){
        //此处添加代码
        this(1);
        System.out.println("Constructor three invoked!");
    }
 
}

1   2

constructor
9
constructor
25

import java.util.*;
 
public class Main {
    public static void main(String[] arsg) {
        Scanner cin = new Scanner(System.in);
        Ring r1 = new Ring(cin.nextDouble() ,cin.nextDouble());
        r1.getArea();
        Ring r2 = new Ring();
        r2.getArea();
    }
}
 
class Ring {
    double innerRadius;
    double outerRadius;
    
    public Ring () {
        this(1 ,3);
    }
    
    public Ring(double innerRadius ,double outerRadius) {
        super();
        this.innerRadius = innerRadius;
        this.outerRadius = outerRadius;
        System.out.println("constructor");
    }
    
    public double getinnerRadius() {
        return innerRadius;
    }
    
    public void setinnerRadius(double innerRadius) {
        this.innerRadius = innerRadius;
    }
    
    public double getouterRadius() {
        return outerRadius;
    }
    
    public void setouterRadius(double outerRadius) {
        this.outerRadius = outerRadius;
    }
    public void getArea() {
        System.out.println((int)(Math.PI * (this.outerRadius * this.outerRadius - this.innerRadius * this.innerRadius)));
    }
}

2   3

Constructor with para
37
Constructor with para
Constructor no para
12

import java.util.*;
 
public class Main {
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        Cylinder res1 = new Cylinder(cin.nextDouble() ,cin.nextDouble());
        res1.getVolumn();
        Cylinder res2 = new Cylinder();
        res2.getVolumn();
    }
}
 
class Cylinder {
 
    private double radius;
    private double height;
 
 
    public Cylinder (double radius ,double height) {
        super();
        System.out.println("Constructor with para");
        this.radius = radius;
        this.height = height;
    }
 
    public void getVolumn() {
        System.out.println((int) (Math.PI * this.radius * this.radius * this.height));
    }
 
    public Cylinder () {
        this.radius = 2;
        this.height = 1;
        System.out.println("Constructor with para");
        System.out.println("Constructor no para");
    }
}

2008 6 12 2009 6 22

6/12/2008 -1

import java.util.*;
 
public class Main {
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        MyDate res1 = new MyDate(cin.nextInt() ,cin.nextInt() ,cin.nextInt());
        res1.print();
        MyDate res2 = new MyDate(cin.nextInt() ,cin.nextInt() , cin.nextInt());
        System.out.print(res1.compare(res2));
    }
}
 
class MyDate {
    int year, math, day;
 
    public MyDate (int year ,int math ,int day) {
        super();
        this.year = year;
        this.math = math;
        this.day = day;
    }
 
    public int getDay() {
        return day;
    }
 
    public void setDay(int day) {
        this.day = day;
    }
 
    public int getMath() {
        return math;
    }
 
    public void setMath(int math) {
        this.math = math;
    }
 
    public int getYear() {
        return year;
    }
 
    public void setYear(int year) {
        this.year = year;
    }
 
    public int compare(MyDate d) {
        if (year > d.year) {
            return 1;
        }
        else if (year < d.year){
            return -1;
        }
        else {
            if (math > d.math) {
                return 1;
            }
            else if (math < d.math) {
                return -1;
            }
            else {
                if (day > d.day) {
                    return 1;
                }
                else if (day < d.day) {
                    return -1;
                }
                else {
                    return 0;
                }
            }
        }
 
    }
 
    public void print() {
        System.out.print(math + "/" + day + "/" + year + " ");
    }
 
}

rwrwewre2345asdJSJQI%^&(&   *&sdf YY( 2342-k'

字母个数：22
数字个数：8
空格个数：5
其他字符个数：10

import java.util.Scanner;
 
public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String str = sc.nextLine();
    sc.close();
    
    char[] chars = str.toCharArray();
    int letter=0,num=0,blank=0,other=0;
    for(int i=0;i<chars.length;i++) {
      if((chars[i]>='A' && chars[i]<='Z') || (chars[i]>='a' && chars[i]<='z')){
        letter++;
      }else if(chars[i]>=47 && chars[i]<=57) {
        num++;
      }else if(chars[i]==32) {
        blank++;
      }else {
        other++;
      }
    }
    
    System.out.println("字母个数："+letter);
    System.out.println("数字个数："+num);
    System.out.println("空格个数："+blank);
    System.out.println("其他字符个数："+other);
  }
}

2 9 0 10

2
9
0
10
10
9
2
0

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        String l = cin.nextLine();
        String[] s = l.split(" ");
        int [] a = new int[s.length];
        for (int i = 0; i < s.length; i++) {
            System.out.println(s[i]);
            a[i] = Integer.parseInt(s[i]);
        }
        int maxn = -0x3f3f3f3f ,minn = 0x3f3f3f3f;
        int f1  = 0,f2 = 0;
        for (int i = 0; i < a.length; i++) {
            if (a[i] > maxn) {
                maxn = a[i];
                f1 = i;
            }
            if (a[i] < minn) {
                minn = a[i];
                f2 = i;
            }
        }
        int temp = a[0];
        a[0] = maxn;
        maxn = temp;
        a[f1] = maxn;
        
        temp = a[s.length - 1];
        a[s.length - 1] = minn;
        a[f2] = temp;
        for (int i = 0; i < s.length; i++) {
            System.out.println(a[i]);
        }
    }
}

小明,2001,Java,88
小刚,2002,Java,78
小丁,2003,Java,56
小宏,2004,Java,85
小明,2001,Python,84
小刚,2002,Python,98
小丁,2003,JavaWeb,66
小宏,2004,Algorithm,87
exit

No1:2002,小刚
No2:2001,小明
No3:2004,小宏
No4:2003,小丁

要求：定义Goods类及其成员变量和方法。
（1）定义Goods类：成员变量有 name,  price 
（2）定义Goods类的带两个参数的构造方法。
（3）定义Goods类的toString()方法，getPrice()方法。

输入5行数据，每行一个商品信息，包括商品名和价格，以一个空格分隔。

输出商品信息，格式：商品名,价格
最后输出总价，格式：should pay:总价

class Main{
    public static void main(String args[]){
        Goods ga[] =new Goods[5];
        Scanner sc = new Scanner(System.in);
        
        for(int i =0;i<5;i++){
            ga[i]= new Goods(sc.next(),sc.nextDouble());
        }        
        
        double  shouldPay = 0;
        for(Goods g:ga){
            shouldPay += g.getPrice();
            System.out.println(g.toString());
        }
        
        System.out.println("should pay:"+shouldPay);            
    }
}

book 5.5 
pencil 1.2 
pen 8.0 
ruler 2.5 
eraser 1.0

book,5.5
pencil,1.2
pen,8.0
ruler,2.5
eraser,1.0
should pay:18.2

import java.util.*;
 
class Goods {
    String name;
    double price;
 
    public Goods(String name, double price) {
        super();
        this.name = name;
        this.price = price;
    }
 
    public double getPrice() {
        return price;
    }
 
    public String toString() {
        return name + "," + price;
    }
}
 
class Main {
    public static void main(String args[]) {
        Goods ga[] = new Goods[5];
        Scanner sc = new Scanner(System.in);
 
        for (int i = 0; i < 5; i++) {
            ga[i] = new Goods(sc.next(), sc.nextDouble());
        }
 
        double shouldPay = 0;
        for (Goods g : ga) {
            shouldPay += g.getPrice();
            System.out.println(g.toString());
        }
 
        System.out.println("should pay:" + shouldPay);
    }
}

（1）成员变量：商品编号（String） 、商品名称(String)、商品单价(double)
（2）成员变量封装，定义为私有属性，并为每个成员变量定义getXXXX，setXXXX方法
（3）定义构造方法，要求带三个参数，参数值用于给成员变量赋值。
（4）重写toString（）方法，将对象转换为字符串，格式：商品编号，商品名称，商品单价

按指定的格式 输入商品信息，调用构造方法生成对象，并输出它。
例：输入：WJ002 记事本 5.5
输出：WJ002,记事本,5.5

WJ002 记事本 5.5

WJ002,记事本,5.5

import java.util.*;
 
class Shangping {
    String num;
    String name;
    double price;
 
    public String getNum() {
        return num;
    }
 
    public double getPrice() {
        return price;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public void setNum(String num) {
        this.num = num;
    }
 
    public void setPrice(double price) {
        this.price = price;
    }
 
    @Override
    public String toString() {
        return num + ',' + name + ',' + price;
    }
 
    public Shangping(String num, String name, double price) {
        this.num = num;
        this.name = name;
        this.price = price;
    }
}
 
class Main {
    public static void main(String args[]) {
        Scanner cin = new Scanner(System.in);
        String l = cin.nextLine();
        String[] s = l.split(" ");
        Shangping res = new Shangping(s[0], s[1], Double.parseDouble(s[2]));
        System.out.println(res.toString());
    }
}

3

-5

this is constructor method
s1:edge=2
s1:area=4
this is constructor method
s2:edge=3
s2:area=9

this is constructor method
s1:edge=2
s1:area=4
this is constructor method
s2:edge=1
s2:area=1

import java.util.Scanner;
class square{
  private int edge;
 
  public int getEdge() {
    System.out.print("s1:edge=");
    return edge;
  }
 
  public square() {
    System.out.println("this is constructor method");
    edge=2;
    this.edge = edge;
    
  }
  public void set(int edge) {
    //System.out.print("s1:edge=");
    if(edge<=0)edge=1;
    this.edge=edge;
  }
  public int get() {
            System.out.print("s2:edge=");
    return edge;
  }
  public int getArea() {
    
    return edge*edge;
  }
}
public class Main{
 
  public static void main(String[] args) {
    square s=new square();
    System.out.println(s.getEdge());
    System.out.print("s1:area=");
    System.out.println(s.getArea());
    
    Scanner in=new Scanner(System.in);
    int x=in.nextInt();
            square s1=new square();
    s1.set(x);
    System.out.println(s1.get());
    System.out.print("s2:area=");
    System.out.println(s1.getArea());
  }}

4
5

-4
-2

this is a constructor
Circle [radius=2]
c1:area=12
this is a constructor
Circle [radius=2]
Circle [radius=4]
c2:area=50
this is a constructor with para
Circle [radius=5]
c3:area=78

this is a constructor
Circle [radius=2]
c1:area=12
this is a constructor
Circle [radius=2]
Circle [radius=2]
c2:area=12
this is a constructor with para
Circle [radius=2]
c3:area=12

import java.util.Scanner;
 
class Circle{
  private int radius;
  public Circle() {
    radius=2;
    System.out.println("this is a constructor");
  }
  public Circle(int radius) {
    if(radius<=0)this.radius=2;
    else this.radius=radius;
    System.out.println("this is a constructor with para");
    
  }
  public void setter(int radius) {
    if(radius<=0)this.radius=2;
    else this.radius=radius;
  }
  public int getter() {
    return radius;
  }
  public int getArea() {
    return (int)(Math.PI*radius*radius);
  }
  public String toString() {
    return "Circle [radius=" + radius + "]";
  }
}
public class Main{
  public static void main(String[] args) {
    Circle c1=new Circle();
    System.out.println(c1.toString());
    System.out.println("c1:area="+c1.getArea());
    Circle c2=new Circle();
    System.out.println(c2.toString());
            //System.out.println("c2:area="+c2.getArea());
    Scanner in=new Scanner(System.in);
    int r=in.nextInt();
    c2.setter(r);
    System.out.println(c2.toString());
     System.out.println("c2:area="+c2.getArea());
    int r1=in.nextInt();
    Circle c3=new Circle(r1);
    System.out.println(c3.toString());
    System.out.println("c3:area="+c3.getArea());
  }
}

this person is lili,her age is 19
this person is lucy,her age is 20

import java.util.*;
public class Main {
    public static void main(String[] args) {
        System.out.println("this person is lili,her age is 19\nthis person is lucy,her age is 20");
    }
}

4 6
6 7

4 5
3 2

Point [x=4, y=6]
false
2

Point [x=4, y=5]
true
3

import java.util.Scanner;
 
interface Comparable {
    void hashcode();
    boolean equals(int x1, int y1, int x2, int y2);
 
}
 
class Point implements Comparable{
    int x;
    int y;
 
    public String ToString(int x,int y) {
        return "Point [x=" + this.x + "," + " y=" + this.y + "]";
    }
 
    public Point() {
        super();
        // TODO Auto-generated constructor stub
    }
 
    public Point(int x,int y) {
        this.x = x;
        this.y = y;
    }
 
    public int getX() {
        return x;
    }
    public void setX(int x) {
        this.x = x;
    }
    public int getY() {
        return y;
    }
    public void setY(int y) {
        this.y = y;
    }
 
    @Override
    public  void hashcode() {
 
    }
 
    @Override
    public boolean equals(int x1,int y1,int x2,int y2) {
        if(x1 >x2) return true;
        else if(x1 < x2) return false;
        else {
            if(y1 >y2) return true;
            else if(y1 < y2) return false;
        }
        return true;
    }
 
    public int distance(Point p1,Point p2) {
        return (int)Math.sqrt(Math.pow(p1.getX() - p2.getX(), 2) + Math.pow(p1.getY()-p2.getY(), 2));
    }
}
 
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int x1,y1;
        x1 = sc.nextInt();
        y1 = sc.nextInt();
        Point point1 = new Point(x1,y1);
        int x2,y2;
        x2 = sc.nextInt();
        y2 = sc.nextInt();
        Point point2 = new Point(x2,y2);
        System.out.println(point1.ToString(x1, y1));
        System.out.println(point1.equals(x1, y1, x2, y2));
        System.out.println(point1.distance(point1,point2));
 
    }
}