java向方法传递对象参数问题？为什么？

Question

入坑小白，自学时遇到问题求大神解答！！！！！

public class Test1 {
    public static void main(String[] args) {
        Circle circle1 = new Circle(1);
        Circle circle2 = new Circle(2);
        swap1(circle1, circle2);
        System.out.println("After swap1: circlel = " + circle1.radius + " circle2 = " + circle2.radius);
        swap2(circle1, circle2);
        System.out.println("After swap2: circlel = " + circle1.radius + " circle2 = " + circle2.radius);
    }
        public static void swap1(Circle x, Circle y) {
            Circle temp = x;
            x = y;
            y = temp; }
        public static void swap2(Circle x, Circle y){
            double temp = x.radius;
            x.radius = y.radius;
            y.radius = temp;
        }

}
            class Circle {
                double radius;

                Circle(double newRadius) {
                    radius = newRadius;
                }
            }

这串代码我运行后结果为

为什么swap1和swap2同样是传入引用类型参数，swap1方法体也创建了一个dui'x来进行交换，而swap1的内容输出后却没有进行交换？

求大神解答！！！！

Answer 1

https://blog.csdn.net/caojidasabi/article/details/80080815