Java-for循环练习

Posted 2021-08-06 师兄白泽

输出四行直角三角形

for (int i = 0; i < 5; i++) {
    for (int j = 0; j < i; j++) {
        System.out.print("*");
    }
    System.out.println();
}

输出七行等腰三角形

for (int i = 0; i < 7; i++) {
    for (int j = 0; j < 7; j++) {
        if (j > i)
            System.out.print(" ");
    }

    for (int j = 0; j < 7; j++) {
        if (j <= i) {
            System.out.print("*");
        }
    }

    for (int j = 0; j < i; j++) {
        System.out.print("*");
    }
    System.out.println("");
}

输出七行棱形

for(int a=1;a<=4;a++){
    for(int b=1;b<=4-a;b++)
        System.out.print(" ");
    for(int c=1;c<=a*2-1;c++)
        System.out.print("*");
    System.out.println();
}
for(int d=3;d>=1;d--){
    for(int b=1;b<=4-d;b++){
        System.out.print(" ");
    }
    for(int c=4-d;c<=2+d;c++){
        System.out.print("*");
    }
    System.out.println();
}

斐波那契数列（for循环实现）

其他的递归和数组以后再讲

a b c c = b+c
1 1 2
int a=1, b=1, c=0;
System.out.println("斐波那契数列前20项为：");
System.out.print(a + "\\t" + b + "\\t");
for (int i = 1; i <= 18; i++) {
    c = a + b;
    a = b;
    b = c;
    System.out.print(c + "\\t");
    if ((i + 2) % 5 == 0)
        System.out.println();
}

冒泡排序

int[] arr = {2, 0, 10, 9, 8, 4, 32, 1, 5, 7};
int invar;
for (int j = 0; j <arr.length-1 ; j++) {
    for (int i = 0; i <arr.length-1-j ; i++) {
        if (arr[i]>arr[i+1]){
            //交换顺序
            invar = arr[i+1];
            arr[i+1] = arr[i];
            arr[i] = invar;
        }
    }
}
System.out.println(Arrays.toString(arr));