想写一个方法来交换main函数中的两个变量值,代码如下:
public class Test {
    public static void swap(int x,int y) {
        int tmp = x;
        x = y;
        y = tmp;
    }
    public static void main(String[] args) {
        int a = 10;
        int b = 20;
        System.out.println("交换前:"+ a +" " + b);
        swap(a,b);
        System.out.println("交换后:"+ a +" " + b);
    }
}运行结果:

解析:并未发生交换,这是因为swap()方法中只改变了形参的值,对实参未进行改变,这些交换只发生在栈上
想要改变实参值,可借用数组交换,也可利用类开辟对象空间,通过传址交换,这些交换发生在堆上
代码示例:
class MyValue{
    public int val;
}
public class Test {
    public static void swap(MyValue myV1,MyValue myV2){
        int temp = myV1.val;
        myV1.val = myV2.val;
        myV2.val = temp;
    }
    public static void main(String[] args) {
        MyValue myValue1 = new MyValue();
        MyValue myValue2 = new MyValue();
        myValue1.val = 1;
        myValue2.val = 2;
        System.out.println("交换前:" + myValue1.val + " " + myValue2.val);
        swap(myValue1,myValue2);
        System.out.println("交换前:" + myValue1.val + " " + myValue2.val);
    }
}解析:

 
 










