Java之for循环嵌套练习

1.打印4层***

*****
*****
*****
*****

class forfor{
    public static void main(String[] args){
        for(int y=0; y<4; y++){
            for(int x=0; x<5; x++){
                System.out.print("*");
            }
            System.out.println();   
        }
    }
}

2.打印5层*，每层递减

*****
****
***
**
*

第一种方法：

class forfor{
    public static void main(String[] args){
        int z=0;
        for(int y=0; y<5; y++){
            for(int x=z; x<5; x++){
                System.out.print("*");
            }
            System.out.println();
            z++;
        }
    }
}

第二种方法：

class forfor{
    public static void main(String[] args) {
        int z=5;
        for (int y=0; y<5; y++) {
                for (int x=z; x>0; x--) {
                    System.out.print("*");
                }
                System.out.println();
                z--;
            }
    }
}

第三种方法，推荐。

class forfor{
    public static void main(String[] args){
        for (int y=0; y<5; y++) {
            for (int x=y; x<5; x++) {
                System.out.print("*");
            }
            System.out.println();
        }
    }
}

3.打印54321，每层递减

54321
5432
543
54
5

class forfor{
    public static void main(String[] args){
        for (int y=0; y<5; y++) {
            for (int x=5; x>y; x--) {
                System.out.print(x);
            }
            System.out.println();
        }
    }
}

4.打印12345，每层递增

1
22
333
4444
55555

class forfor{
    public static void main(String[] args){
        for (int y=1; y<=5; y++) {
            for (int x=1; x<=y; x++) {
                System.out.print(y);
            }
            System.out.println();
        }

    }
}

5.九九乘法表

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

class forfor{
    public static void main(String[] args){
        for (int y=1; y<=9; y++) {
            for (int x=1; x<=y; x++) {
                System.out.print(x+"x"+y+"="+x*y+"\t");// \t:制表符
            }
            System.out.println();
        }

    }
}

6.打印倒三角形

      ******* 
       ***** 
        *** 
         * 

class forfor{
    public static void main(String[] args){
        for (int y=1; y<=5; y++) {
            for (int x=1; x<y; x++) {
                System.out.print(" ");
            }
            for (int z=y; z<=5; z++) {
                System.out.print("* ");
            }
            System.out.println();
        }

    }
}