代码

import javax.management.MalformedObjectNameException;
import java.util.Scanner;
public class Bank {
    public String Banker;
    public long BankNum;
    public double Balance;
    public Bank(String man,long num,double money)
    {
        Banker= man;
        BankNum=num;
        Balance=money;
    }
    public double CheckBalance() {
        return Balance;
    }
    public void Deposit(double a) {
        Balance+=a;
    }
    public Boolean Withdrawal(double money) {
        if(money>Balance)
            return false;
        Balance-=money;
        return true;
    }
    public void Operation(){
        Scanner In=new Scanner(System.in);
        System.out.println(Banker+"先生您好！");
        System.out.println("查询余额请按：1  存款请按：2  取款请按：3  结束请按：0");
        int select=1;
        while(select!=0)
        {
            select=In.nextInt();
            switch (select)
            {
                case 0:
                    System.out.println("感谢您的使用！！！");
                    break;
                case 1://查询余额
                    System.out.println("余额："+this.CheckBalance());
                    break;
                case 2://存钱
                    System.out.print("输入存款金额:");
                    Double a=In.nextDouble();
                    this.Deposit(a);
                    break;
                case 3://取钱
                    System.out.print("输入取款金额:");
                    Double m=In.nextDouble();
                    Boolean T = this.Withdrawal(m);
                    if(T)
                        System.out.println("Withdrawal completed!!!");
                    else
                        System.out.println("Insufficient balance!!!");
                    break;
                default:
                    System.out.println("输入不合法，请重新输入！！");
            }
        }
    }
    public static void main(String[] args) {
        Bank Banker1=new Bank("张三",1012468689,25415.2651);
        Bank Banker2=new Bank("李四",245144654,35694.2651);
        Banker1.Operation();
        System.out.println("_________________");
        Banker2.Operation();
    }
}

public class Triangle {
    public int A;
    public int B;
    public int C;
    public void Set(int a,int b,int c){
        this.A=a;
        this.B=b;
        this.C=c;
    }
    public double GetArea(){
        double p=(A+B+C)/2;
        double Area=Math.sqrt((p*(p-A)*(p-B)*(p-C)));
        return Area;
    }
    public double GetAround() {
        return (A+B+C);
    }
    public static void main(String[] args) {
        Triangle t1=new Triangle();
        t1.Set(3,4,5);
        System.out.println("t1的面积为："+t1.GetArea());
        System.out.println("t1的周长为："+t1.GetAround());
        Triangle t2=new Triangle();
        t2.Set(7,8,9);
        System.out.println("t2的面积为："+(String.format("%.4f",t2.GetArea())));
        System.out.println("t2的周长为："+t2.GetAround());
    }
}

import java.util.Scanner;
public class Student {
    public String No;
    public String Name;
    public int Age;
    //static int num=0;
    public Student(String no,String name,int age){
        No =no;
        Name=name;
        Age=age;
    }
    public void display(){
        System.out.print("学号：："+No);
        System.out.print("  姓名：："+Name);
        System.out.println("  年龄：："+Age);
    }
    public void Addage(){
        Age+=1;
    }
    public static void main(String[] args) {
        // Scanner In=new Scanner(System.in);
        Student s[]=new Student[5];
        s[0]=new Student("001","张三",18);
        s[1]=new Student("002","李四",19);
        s[2]=new Student("003","王五",20);
        s[3]=new Student("004","小明",21);
        s[4]=new Student("005","小红",18);
        for(int i=0;i<5;i++)
            s[i].display();//显示信息
        System.out.println("___________________________________");
        for(int i=0;i<5;i++)//年龄加1
            s[i].Addage();
        for(int i=0;i<5;i++)//年龄加1后输出
            s[i].display();
        System.out.println("_________输出年龄大于20的学生________");
        for(int i=0;i<5;i++){//年龄加1后输出
            if(s[i].Age>=20)
                s[i].display();
        }
    }
}

import java.util.Scanner;
public class Data {
    public int Year;
    public int Month;
    public int Day;
    //
    Data(int y,int m,int d){
        Year=y;
        Month=m;
        Day=d;
    }
    public boolean IsLeapYear()
    {
        if((Year%4==0&&Year%100!=0)||(Year%400==0))
            return true;
        return false;
    }
    public boolean Check(){
        if(Month<1||Month>12)
            return false;
        if((Month==1||Month==3||Month==5||Month==7||Month==8||Month==10||Month==12)&&(Day<1||Day>31))
            return false;
        if((Month==4||Month==6||Month==9||Month==11)&&(Day<1||Day>30))
            return false;
        if((Month==2&&this.IsLeapYear())&&(Day<1||Day>29))
            return false;
        if((Month==2&&(!this.IsLeapYear()))&&(Day<1||Day>28))
            return false;
        return true;
    }
    public static void main(String[] args) {
        while(true) {
            Scanner In=new Scanner(System.in);
            int y=In.nextInt();
            int m=In.nextInt();
            int d=In.nextInt();
            Data D=new Data(y,m,d);
            if(D.Check())
                System.out.println(y+"/"+m+"/"+d);
            else
                System.out.println("输入不合法");
        }
    }
}