Trim for null string

[laosu]

Hi,

Please help.
Why we will getting NullPointerException when we trying to trim a NULL string,
but won't be getting error if we trim a string with "".

Example: string a= null; System.out.println(a.trim()); -> NullPointerException
string b= ""; System.out.println(b.trim()); -> No error


Thanks..

[Fubarable]

There's no such thing as a null string. There is only null, a variable that refers to no object, nothing. So what happens here is the same thing that happens when you try to call any method of a null. This shouldn't come as a surprise.

[laosu]

Got it, thanks for your reply.

If i have a string variable that get the NULL value from database, what is the best way to check before to trim it?

[Fubarable]

Got it, thanks for your reply.

If i have a string variable that get the NULL value from database, what is the best way to check before to trim it?

if (myString != null) {
  myString = myString.trim();
}

// or

myString = (myString == null) ? null : myString.trim();