问题
When should one compare Strings as objects and when should one use their equals method? To make sure, I always use equals, but that doesn\'t seem very efficient. In what situations can I be certain that string1 == string2 is a safe to use?
Thanks!
回答1:
You should almost always use equals. You can be certain that string1 == string2 will work if:
- You've already made sure you've got distinct values in some other way (e.g. you're using string values fetched from a set, but comparing them for some other reason)
- You know you're dealing with compile-time string constants
- You've manually interned the strings yourself
It really doesn't happen very often, in my experience.
回答2:
From what I know of Java, string1==string2 will only be true if the references to those objects are the same. Take a look at the following case
String string1 = new String("Bob");
String string2 = new String("Bob");
string1 == string2; // false, they are seperate objects
string1 = string2; // asigning string1 to string2 object
string1 == string2; // true, they both refer to the same object
回答3:
You can only use the == for comparison if you are sure the objects are the same.
For example, this could occur if you had a final static String variable. You could be certain that a comparison would be between the same object.
Stick with the equals for string comparison.
来源：https://stackoverflow.com/questions/3885753/string-comparison-and-string-interning-in-java