求100以内所有偶数和

1.for循环
public class Demo1 {
    public static void main(String[] args){
        int sum = 0;
        for(int i = 0;i<= 100;i++){
            if(i%2 == 0){
                sum += i;
            }
        }
        //输出1-100内的所有偶数之和.
        System.out.println(sum);
    }
}

2.while循环

public class Demo4 {
    public static void main(String[] args){
        int sum = 0;
        int i = 0;
        while(i<=100){
            i++;
            if(i%2 == 0) {
                sum += i;
            }
        }
        //输出100以内所有偶数和
        System.out.println(sum);
    }
}


3.do-while循环

public class Demo5 {
    public static void main(String[] args) {
        int sum = 0;
        int i = 1;
        do {
            i++;
            if(i%2 == 0) {
                sum += i;
            }
        } while (i <= 100);
        //输出100以内所有偶数和
        System.out.println(sum);
    }
}