Java - Coding Style : What are the cons and pros of "ABC".equals("SOMESTRING") style string comparison? [duplicate]

Question

Let me first start-of with a sample code...

String password = "";

if("PIRATE".equals(password)) {
     // Do something
}

See here, the String constant or literal (whatever) "PIRATE" is used to check the equality of the two Strings. Whereas...

String password = "";
if(password.equals("PIRATE")) {
     // Do something
}

this also works exactly as the previous code.

Now-a-days, I see a lot of the first style "STRING_LITERAL".equals(STRING_OBJECT), while Java people post code.

So my question is, Where does this style comes from ? and Is it better than the second style in any way ?

In-fact i find the second style more logical than the first one, why ?!

lets take a requirement like, if the user-provided-password is equal to the "PIRATE" then give permission to that user

when you start implementing the above requirement,

String userProvidedPassword = getPaswordFromUser();

if(userProvidedPassword.equals("PIRATE")) {
 // Allow him
}

Doesn't this more logical than "PIRATE".equals(userProvidedPassword); ?! Just think about it...

Correct me if I'm wrong.. Thanks..

---

EDIT : Sorry, this question didn't come up in my previous search, and it answers my question perfectly. Also thanks to all those who helped out here..

Answer 1

"PIRATE".equals(password) cannot result in a NullPointerException.

whereas

password.equals("PIRATE") will throw a NullPointerException if password happens to be null.

Therefore the use of the former is encouraged : it is safer.

Answer 2

When you write password.equals("PIRATE") you are almost asking for a NullPointerException ,where there are chances for password might null.

It's all about Avoiding NullPointerException.

if("PIRATE".equals(password)) {
     // Do something
}

Avoids NullPointerException

where as

if(password.equals("PIRATE")) {
     // Do something
}

thrwos you NullPointerException if password is null.

However ,Personally I feel this is looks odd in middle of the code. and I always prefer to write

if(password !=null && password.equals("PIRATE") ){

//do something 

}

Answer 3

The only con is really a style problem. Saying "PIRATE".equals(password) is called a Yoda Condition. However, as people have already stated, it is safer to use that kind of condition (so I would keep using that kind).