Checking if a string is empty or null in Java [duplicate]
I'm parsing HTML data. The String
may be null
or empty, when the word to parse does not match.
So, I wrote it like this:
if(string.equals(null) || string.equals("")){
Log.d("iftrue", "seem to be true");
}else{
Log.d("iffalse", "seem to be false");
}
When I delete String.equals("")
, it does not work correctly.
I thought String.equals("")
wasn't correct.
How can I best check for an empty String
?
Solution 1:
Correct way to check for null or empty or string containing only spaces is like this:
if(str != null && !str.trim().isEmpty()) { /* do your stuffs here */ }
Solution 2:
You can leverage Apache Commons StringUtils.isEmpty(str)
, which checks for empty strings and handles null
gracefully.
Example:
System.out.println(StringUtils.isEmpty("")); // true
System.out.println(StringUtils.isEmpty(null)); // true
Google Guava also provides a similar, probably easier-to-read method: Strings.isNullOrEmpty(str)
.
Example:
System.out.println(Strings.isNullOrEmpty("")); // true
System.out.println(Strings.isNullOrEmpty(null)); // true
Solution 3:
You can use Apache commons-lang
StringUtils.isEmpty(String str)
- Checks if a String is empty ("") or null.
or
StringUtils.isBlank(String str)
- Checks if a String is whitespace, empty ("") or null.
the latter considers a String which consists of spaces or special characters eg " " empty too. See java.lang.Character.isWhitespace API