循环

1.while循环

package com.kuang.struct;

public class WhileDemo01 {
    public static void main(String[] args) {
        //输出1-100
        int i = 0;
        while(i<100){
            i++;
            System.out.println(i);
        }
    }
}

package com.kuang.struct;

public class WhileDemo02 {
    public static void main(String[] args) {
        //死循环
        while (true){
            //客户端等待连接
            //闹钟计时
        }
    }
}

package com.kuang.struct;

public class WhileDemo03 {
    public static void main(String[] args) {
        //计算 1+2+3+4+····100
       int i = 0;
       int sum = 0;

       while (i<=100){
           sum+=i;
           i++;
       }
        System.out.println(sum);
    }
}

2.Do while循环

package com.kuang.struct;

public class DoWhileDemo01 {
    public static void main(String[] args) {
        int i = 0;
        int sum = 0;
        do {
            sum+=i;
            i++;
        }while (i<=100);
        System.out.println(sum);
    }

}

3.For循环

package com.kuang.struct;

public class ForDemo02 {
    public static void main(String[] args) {
        //练习1，计算0-100奇数和偶数的和
        int oddSum = 0;
        int evenSum = 0;
        for (int i = 0; i <= 100; i++) {
            if(i%2!=0){
                oddSum+=i;
            }else{
                evenSum+=i;
            }
        }
        System.out.println("奇数的和:"+oddSum);
        System.out.println("偶数的和"+evenSum);
    }
}

package com.kuang.struct;

public class ForDemo03 {
    public static void main(String[] args) {
        //练习2:for循环输出1-1000能被5整除的数，并且每行输出3个
        for (int i = 0; i < 1000; i++) {
            if(i%5==0){
                System.out.print(i+"\t");
            }
            if(i%(5*3)==0){//每行
                System.out.println();
            }
            //println输出完会换行
            //print 输出完不会换行
        }
    }
}

package com.kuang.struct;

public class ForDemo04 {
    //练习3 打印九九乘法表
    /*
1*1=1
1*2=2  2*2=4
1*3=3  2*3=6  3*3=9
1*4=4  2*4=8  3*4=12 4*4=16
1*5=5  2*5=10 3*5=15 4*5=20 5*5=25
1*6=6  2*6=12 3*6=18 4*6=24 5*6=30 6*6=36
1*7=7  2*7=14 3*7=21 4*7=28 5*7=35 6*7=42 7*7=49
1*8=8  2*8=16 3*8=24 4*8=32 5*8=40 6*8=48 7*8=56 8*8=64
1*9=9  2*9=18 3*9=27 4*9=36 5*9=45 6*9=54 7*9=63 8*9=72 9*9=81
     */
    public static void main(String[] args) {
        for (int i = 1; i <= 9; i++) {
            for (int j = 1; j <= i; j++) {
                System.out.print(j+"*"+i+"="+(j*i)+"\t");
            }
            System.out.println();

        }
    }
}

4.增强for循环

package com.kuang.struct;

public class ForDemo05 {
    public static void main(String[] args) {
        int[] numbers = {10,20,30,40,50};
        //遍历数组元素
        for(int x:numbers){
            System.out.println(x);
        }
    }
}

5.break和continue

package com.kuang.struct;

public class ContinueDemo {
    public static void main(String[] args) {
        for (int i =0;i<100;i++){
            if (i%10==0){
                System.out.println();
                continue;
            }
            System.out.println(i);
        }
    }
}

6.打印三角形

package com.kuang.struct;

public class TestDemo {
    public static void main(String[] args) {
        //打印三角形  5行
        for (int i = 1; i <= 5; i++) {
            for (int j =5;j>=i;j--){
                System.out.print(" ");
            }

            for (int j = 1;j<=i;j++){
                System.out.print("*");
            }
            for (int j = 1;j<i;j++){
                System.out.print("*");
            }
            System.out.println();
        }


    }
}