Java 按引用传递与按值传递的麻烦

Question

为什么我在传递引用示例中遇到错误 obj1.add200really 带有下划线

public class Test {

    private int number;

    Test(){
        number = 1;
    }

    public static void main(String[] args) {
        Test obj1 = new Test();
        System.out.println("the number is " + obj1.number);
        System.out.println("the number 1 plus 200 is " + obj1.add200(obj1.number));
        System.out.println("while the number is still " + obj1.number);
        System.out.println("\n");
        System.out.println("the number is " + obj1.number);
        System.out.println("the number 1 plus 200 is " + obj1.add200really(obj1.number));
        System.out.println("while the number is still " + obj1.number);
    }


int add200(int somenumber){
    somenumber = somenumber + 200;
    return somenumber;
}
int add200really(Test myobj){
    myobj.number = 999;
    return myobj.number;
}
}

Answer 1

使用obj1.add200really(obj1);