自学JAVA,请教问题,求指点

public class Demo12HundredSum{
    public static void main(String[] args){
        int sum = 0;
        
        for(int i = 1;i <=100;i++){
            if (i %2 == 0){
                sum += i;
            }
        }
        System.out.println("结果是:" + sum);
        System.out.println("=============");
        
        int i = 1;
        while(i <= 100){
            if (i %2 == 0){
            sum += i;
            }
                i++;
        }
        System.out.println("结果是:" + sum);
        System.out.println("=============");
        
        int i = 1;
        do{
            if(i %2 == 0){
            sum += i;
            }
                i++;
        }while(i <= 100);
        System.out.println("结果是:" + sum);   
            }   
        }
        
        

 练习语句转换,