JAVA while循环，do-while循环，for循环

public class Test{
    public static void main(String[] args){
        int i    =    1;
        while(i<30){
            System.out.println(i);
            i++;
        }
    }
}

public class Test{
    public static void main(String[] args){
        int i    =    1;
        do{
            System.out.println(i);
            i++;
        }
        while(i<30);
        //do-while循环，先执行一次，然后在判断，如果条件成立，在循环执行，如果不成立，继续往下执行
    }
}

import java.util.*;
public class Test{
    public static void main(String[] args){
        Scanner    in    =    new Scanner(System.in);
        Random    ra    =    new Random();
        int r    =    ra.nextInt(10);
        int j;
        System.out.println("=======猜数字游戏=======");
        do{
            System.out.println("请输入要猜数字（0-9）：");
            int num    =    in.nextInt();
            if(num<r){
                System.out.println("小了");
                j    =    1;
            }
            else if(num>r){
                System.out.println("大了");
                j    =    2;
            }
            else{
                System.out.println("猜对");
                j    =    11;
            }
        }
        while(j!=11);
    }
}

public class Test{
    public static void main(String[] args){
        for(int i=1;i<30;i++){
            System.out.println(i);
        }
    }
}