为什么前面可以用int，后面关于“three”的计算不能用int？？？？

public class HelloWorld{

    public static void main(String[] args) {

   int one = 10 ;

        int two = 20 ;

        int three = 30 ;

        three +=three+one;

        three -=three-one;

        three *=three+one;

        three /=three/one;

        three %=three%one;

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

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

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

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

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

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

}

}