辨异 —— Java 中 String 的相等性比较

How do I compare strings in Java?

1. 语法知识

• ==：判断的是引用的相等性（reference equality），也即是否为同一对象；
• .equals()：判断的是值的相等性（value equality），也即是否在逻辑上相等；

2. 举例

• new String(“test”).equals(“test”) // –> true
  • // These two have the same value
• new String(“test”) == “test” // –> false
  
  • // … but they are not the same object
  • new String(“test”) == new String(“test”) // –> false
• “test” == “test” // –> true
  
  • literals are interned by the compiler and thus refer to the same object
• Objects.equals(“test”, new String(“test”)) // –> true
  
  • Objects.equals(null, “test”) // –> false
  • // … but you should really just call Objects.equals()