一直显示错误

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);

   }
}