Home Java javaTutorial Detailed explanation of the differences between equals(), equalsIgnoreCase() and == in Java

Detailed explanation of the differences between equals(), equalsIgnoreCase() and == in Java

May 23, 2017 am 10:55 AM

用久了C#,在Java中,判断一个字符串还是习惯性的用了==,但是总是不能按照正确的判断分支运行,后来才想起来Java中是有equals的,然后就有引出了equalsIgnoreCase。
这三种的正确运用能对敲代码的时候减少不少烦躁的机会。
一、==
==是最经典的判断,此符号判断的是两个对象的值,即对象的内存地址。

[java]String s1 = new String("abc");
String s2 = new String("abc");
System.out.println(s1 == s2);
[/java]
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这两个字符串字符是相同的,但是内存地址不同,用==判断输出结果是:false;
二、equals和equalsIgnoreCase
equals是Object的方法,用来判断两个对象是否相同,在判断字符串时它判断的是两个对象的内容是否相同。
equalsIgnoreCase是String的判断方法,只能判断两个字符串。

[java]
String s1 = new String("abc");
String s2 = new String("Abc");
System.out.println(s1.equals(s2));
System.out.println(s1.equalsIgnoreCase(s2));
[/java]
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上面的例子中,输出结果为:false true
equalsIgnoreCase大小写不敏感 equals大小写敏感。
引申:

如果第一个例子写成这样:

[java]
String s1 = "abc";<
String s2 = "abc";
System.out.println(s1 == s2);
[/java]
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输出结果就会是:True。
这是为什么呢?
在声明变量的时候,如果用=直接赋值,此时如果变量池中有相同值的字符串,那么就会直接把这个对象的地址赋给新的变量。
而new String("abc")则会重新生成一个变量地址。

【相关推荐】

1. 分享Java中equals和equalsignorecase的区别及使用实例教程

2. 介绍Java equalsIgnoreCase()方法实例

3. java中equalsIgnoreCase方法的图文实例

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