英语原文地址：https://www.javaguides.net/2020/03/java-program-to-swap-two-strings.html 作者：Ramesh Fadatare 翻译：高行行

在这篇快速文章中，我们将看到如何编写Java程序以在使用或不使用第三个变量的情况下交换两个字符串。

首先，我们将看到如何编写Java程序以使用第三个变量交换两个字符串，然后，我们将看到如何编写Java程序以不使用第三个变量交换两个字符串。

1. Java程序用第三个变量交换两个字符串

package com.java.tutorials.programs;
public class SwapTwoStrings {
    public static void main(String[] args) {
        String s1 = "java";
        String s2 = "guides";
        System.out.println(" before swapping two strings ");
        System.out.println(" s1 => " + s1);
        System.out.println(" s2 => " + s2);
        String temp;
        temp = s1; // java
        s1 = s2; // guides
        s2 = temp; // java
        System.out.println(" after swapping two strings ");
        System.out.println(" s1 => " + s1);
        System.out.println(" s2 => " + s2);
    }
}

Output:

 before swapping two strings 
 s1 => java
 s2 => guides
 after swapping two strings 
 s1 => guides
 s2 => java

2. Java程序不使用第三个变量交换两个字符串

Refer the comments which are self descriptive.

package com.java.tutorials.programs;
/**
 * Java程序不使用第三个变量交换两个字符串
 * @author Ramesh Fadatare
 *
 */
public class SwapTwoStrings {
    public static void main(String[] args) {
        String s1 = "java";
        String s2 = "guides";
        System.out.println(" before swapping two strings ");
        System.out.println(" s1 => " + s1);
        System.out.println(" s2 => " + s2);
        // 第一步: concat s1 + s2 and s1
        s1 = s1 + s2; // javaguides // 10  
        // 第二步: 将 s1 的初始值存储到 s2 中
        s2 = s1.substring(0, s1.length() - s2.length()); // 0, 10-6 //java
        // 第三步: 将 s2 的初始值存储到 s1 中
        s1 = s1.substring(s2.length());
        System.out.println(" after swapping two strings ");
        System.out.println(" s1 => " + s1);
        System.out.println(" s2 => " + s2);
    }
}

Output:

 before swapping two strings 
 s1 => java
 s2 => guides
 after swapping two strings 
 s1 => guides
 s2 => java