为什么不对 总是提示错误

public class HelloWorld{

    public static void main(String[] args) {

   int one=10;

        int two=20;

        int three=0;

        three=one+two;

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

        three+=one;

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

        three-=one;

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

        three*=one;

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

        three/=one;

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

        three%=one;

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