for 循环的进阶用法

求100以内奇数偶数和

public class forDemo2 {
    public static void main(String[] args) {
        //0到100奇数和偶数的和
        int oddSum = 0;
        int eveSum = 0;
        for (int i = 0; i <= 100; i++) {
            if (i % 2 == 0) {
                oddSum += i;
            } else {
                eveSum += i;
            }
        }
        System.out.println("奇数的和为："+oddSum);
        System.out.println("偶数的和为："+eveSum);
        System.out.println("总和为："+oddSum+eveSum);
    }
}

用while或for循环输出1-1000之间能被5整除的数，并且每行输出3个

public class forDemo3 {
    public static void main(String[] args) {
        //用while或for循环输出1-1000之间能被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%15==0){
                System.out.println();
                //System.out.println("/n");
            }
        }
        System.out.println("============================");
        int a=0;
        while (a<=1000){
            a++;
            if(a%5==0){
                System.out.print(a+"\t");
            }
            if(a%15==0){
                System.out.println();
            }
        }
    }
}

打印九九乘法表

public class forDemo4 {
    public static void main(String[] args) {
        for (int i = 1; i <=9; i++) {
            for (int j = 1; j <= i; j++) {
                System.out.print(i+"*"+j+"="+(i*j)+"\t");
            }
            System.out.println();

        }
    }
}

遍历数组元素

public class forDemo5 {
    public static void main(String[] args) {
        int[] number={1,2,3,4,5};
        for (int x:number) {
            System.out.println(x);
        }
    }
}

打印三角形

public class LabeDemo1 {
    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();
        }
    }
}

打印爱心

public class heart {
    public static void main(String[] args) {
        int i, j;
        for(i = 0; i < 3; i++){
            for (j = 5; j > 2 * i; j--){
                System.out.print(" ");
            }
            for (j = 0; j < 4 * i + 5; j++){
                System.out.print("*");
            }
            for (j = 0; j < 9 - 4 * i; j++){
                System.out.print(" ");
            }
            for (j = 0; j < 4 * i + 5; j++){
                System.out.print("*");
            }
            System.out.println();
        }
        for (i = 0; i < 3; i++){
            for (j = 0; j < 29; j++){
                System.out.print("*");
            }
            System.out.println();
        }
        for (i = 0; i < 7; i++) {
            for (j = 1; j <= 2 * i +1; j++){
                System.out.print(" ");
            }
            for (j = 27; j > 4 * i; j--){
                System.out.print("*");
            }
            System.out.println();
        }
        for (i = 0; i < 14; i++) {
            System.out.print(" ");
        }
        System.out.println("*");
    }
}

输出结果