Java：为什么这种交换方法不起作用？ [英] Java: Why does this swap method not work?

问题描述

我有以下代码：

public class Main {

    static void swap (Integer x, Integer y) {
        Integer t = x;
        x = y;
        y = t;
    }

    public static void main(String[] args) {
       Integer a = 1;
       Integer b = 2;
       swap(a, b);
       System.out.println("a=" + a + " b=" + b);
    } 
}

我希望它打印a = 2 b = 1 ，但它打印相反。显然交换方法不会交换a和b值。为什么？

I expect it to print a=2 b=1, but it prints the opposite. So obviously the swap method doesn't swap a and b values. Why?

推荐答案

这与整数的不变性无关;它与 Java是按值传递这一事实有关，该死！ （没有恼火，只是文章的标题：p）

This doesn't have anything to do with immutability of integers; it has to do with the fact that Java is Pass-by-Value, Dammit! (Not annoyed, just the title of the article :p )

总结：你不能真正做到Java中的swap方法。你只需要自己做交换，无论你需要什么;这只是三行代码，所以不应该是一个很大的问题：）

To sum up: You can't really make a swap method in Java. You just have to do the swap yourself, wherever you need it; which is just three lines of code anyways, so shouldn't be that much of a problem :)

    Thing tmp = a;
    a = b;
    b = tmp;

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