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();
        }

    }
}