演示与Java的字符串比较 [英] Demonstrating string comparison with Java

问题描述

我想演示一下几行代码，在Java中，要比较两个字符串（ String ），你必须使用 equals （）而不是运算符 == 。

I want to demonstrate with a few line of code that in Java, that to compare two strings (String), you have to use equals() instead of the operator ==.

public static void main(String Args[]) {
   String s1 = "Hello";
   String s2 = "Hello";

   if (s1 == s2)
      System.out.println("same strings");
   else
      System.out.println("different strings");
}

我期待这个输出： code>，因为测试 s1 == s2 我实际上是比较两个引用（即地址）而不是对象的内容。

I was expecting this output : different strings, because with the test s1 == s2 I'm actually comparing two references (i.e. addresses) instead of the objet's content.

但我实际上有这个输出：相同的字符串！

But I actually got this output : same strings !

浏览互联网我发现一些Java实现将优化上述代码，使 s1 和 s2

Browsing the internet I found that some Java implementation will optimize the above code so that s1and s2 will actually reference the same string.

那么，当比较字符串时，如何使用 == （or Objects）in Java？

Well, how can I demonstrate the problem using the == operator when comparing Strings (or Objects) in Java ?

推荐答案

编译器在你的情况下做一些优化，使 s1 和 s2 都是同一个对象。你可以使用

The compiler does some optimizations in your case so that s1 and s2 are really the same object. You can work around that by using

String s1 = new String( "Hello" );
String s2 = new String( "Hello" );

然后你有两个不同的对象，文本内容相同。

Then you have two distinct objects with the same text content.

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