要比较UUID，可以使用==还是必须使用UUID.equals(UUID)? [英] To compare UUID, can I use == or have to use UUID.equals(UUID)?

问题描述

只需开始使用 java.util.UUID .我的问题是，如果我有两个UUID变量，例如u1和u2，并且我想检查它们是否相等，我可以安全地使用表达式 u1 == u2 还是必须编写 u1.equals(u2)?假设两者都不为空.

Just start using java.util.UUID. My question is if I have two UUID variables, say u1 and u2, and I would like to check if they are equal, can I safely use expression u1 == u2 or have to write u1.equals(u2)? assuming both are not null.

顺便说一句，我正在使用其 randomUUID 方法创建新的UUID值，但是我认为这无关紧要.我想知道UUID是唯一的，每个值都可以是一个单例，那么使用 u1 == u2 是安全的.

BTW, I am using its randomUUID method to create new UUID values, but I think this should not be matter. I wonder as UUID is unique, each value could be a singleton, then it is safe to use u1 == u2.

void method1(UUID u1, UUID u2) {

   // I know it is always safe to use equal method
   if (u1.equals(u2)){ 
     // do something
   }

   // is it safe to use  ==
   if (u1 == u2) {
     // do something
   }
}

推荐答案

这取决于:您想要哪种平等类型?

It depends: which type of equality do you want?

UUID a = new UUID(12345678, 87654321);
UUID b = new UUID(12345678, 87654321);
UUID c = new UUID(11111111, 22222222);

System.out.println(a == a); // returns true
System.out.println(a.equals(a)); // returns true

System.out.println(a == b); // returns false
System.out.println(a.equals(b)); // returns true

System.out.println(a == c); // returns false
System.out.println(a.equals(c)); // returns false

仅当 a 和 b 是同一对象时，

a == b 是true.如果它们是两个相同的对象，它将仍然是false.

a == b is true only if a and b are the same object. If they are two identical objects, it will still be false.

a.equals(b)为true.

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