How to check a string that not empty in java?

Question

How to check a string in java that is empty or not?

For example : string str = " " and string str2 = " " and str3 = ""

str includes 3 spaces, str2 includes 1 space, and str3 has no characters but all of them are empty.

How do I check this in Android?

They are both equal to some string and null at the same time? — ChiefTwoPencils, Apr 08 '15 at 22:04
THey are not null. They are empty. There's a big difference. — Gabe Sechan, Apr 08 '15 at 22:05
No @Programmer NULL and empty are two separate concepts in Java. Learn that quickly or you'll be both confused and writing buggy code — Gabe Sechan, Apr 08 '15 at 22:06
Empty string `""` , string with spaces `" "` and `null` string are 3 different things — Shrikant Havale, Apr 08 '15 at 22:09
well your question is marked as duplicate and it indeed is, and answer to your question can be found at the top , where it says `This question already has an answer here:` — Shrikant Havale, Apr 08 '15 at 22:18

user370305 · Answer 1 · 2015-04-08T22:22:46.047

3

Just check with str.isEmpty() as isEmpty() method will return true for actual length if 0.

As NULL refers to memory assignment of your String str. To check empty String use isEmpty() method.

Update:

In your case, best scenario should be,

if(str != null && str.trim().length() > 0)
{
     // String str is not NULL or not Empty
}else
{
    // String str is NULL or Empty
}

edited Apr 08 '15 at 22:22

answered Apr 08 '15 at 22:06

user370305

@Sotirios Delimanolis - Woops Its my Mistake. Corrected. – user370305 Apr 08 '15 at 22:18

Dopdop · Answer 2 · 2015-04-08T22:17:54.863

0

Null != empty. Null means the variable is not initialized, like: String s; Your str,str2 and str3 are initialized, zo they are not null.

To check for same characters: str.equals("foo"), ("foo" is in your case spaces :) )

NOT str == "foo". The last means you're checking same references.

edited Apr 08 '15 at 22:17

answered Apr 08 '15 at 22:08

Dopdop

score -2 · Accepted Answer · answered Apr 08 '15 at 22:06

-2

You can see if the characters match

if (str.equals ("")) {
  // true
}

if (str3.equals ("   ")) {
  // true
}

answered Apr 08 '15 at 22:06

jb15613

Think I misunderstood his question... – jb15613 Apr 08 '15 at 22:10
I guess so, question is not clear, if he wants to compare empty strings or null strings – Shrikant Havale Apr 08 '15 at 22:12
3

You can always edit or delete your answer. – Sotirios Delimanolis Apr 08 '15 at 22:15

3 Answers3