楼上说的是一个问题，另外，不太建议这样用，浪费内存

public class HelloWorld{

    public static void main(String[] args) {

   int one = 10 ;

        int two = 20 ;

        int three = 0 ;

        int sum = one + two;

        three = sum;

        int s1 = three += one;

        int s2 = three -= one;

        int s3 = three *= one;

        int s4 = three /= one;

        int s5 = three %= one;

        System.out.println("three = one + two ==>" + sum);

        System.out.println("three += one ==>" + s1);        

        System.out.println("three -= one ==>" + s2);      

        System.out.println("three *= one ==>" + s3);        

        System.out.println("three /= one ==>" + s4);        

        System.out.println("three %= one ==>" + s5);      

        }

}

输出语句里面的逗号改成加号