字符串处理：==的用法 [英] String handling: Usage of ==

问题描述

您能否在下面的代码中进行解释：

Could you pls explain on the below code:

我知道 == 会比较引用而不是引用价值 。
但是我不清楚下面的代码到底发生了什么？

I know that == compares the reference and not the values . But I am not clear what exactly is happening on the below code?

    public class StringEquals {
    public static void main(String args[])
    {

        String s1="AB";
        String s2="AB"+"C";
        String s3="A"+"BC";
        if(s1==s2)
        {
            System.out.println("s1 and s2 are equal");
        }
        else
        {
            System.out.println("s1 and s2 are notequal");
        }
        if(s2==s3)
        {
            System.out.println("s2 and s3 are equal");
        }
        else
        {
            System.out.println("s2 and s3 are notequal");
        }
        if(s1==s3)
        {
            System.out.println("s1 and s3 are equal");
        }
        else
        {
            System.out.println("s1 and s3 are notequal");
        }   
    }
    }

推荐答案

在Java中， == 检查两个对象是否完全相同，有时它的行为与您的想法不符。

In Java, == checks if two objects are exactly same thing, sometime it acts not what you think.

String s1 = new String("AB")
String s2 = new String("AB")

尽管 s1 和 s2 具有相同的内容，但是 s1 == s2 返回 false 。因为它们具有不同的引用，但是 s1 s2 具有相同的值，因此 s1.equals（s2）返回 true

Although s1 and s2 have the same content, but s1 == s2 returns false. Because they have different reference, But s1 s2 have same value so s1.equals(s2) returns true

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