Java中的赋值运算符

public class HelloWorld{

    public static void main(String[] args) {

   int one = 10 ;

        int two = 20 ;

        int three = 0 ;

        three = one+two;

        three += one;

        three -= one;

        three *= one;

        three /= one;

        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);

}

}

为什么等于0 而且还能下一章节