StringUtils.isBlank() checks that each character of the string is a whitespace character (or that the string is empty or that it's null). This is totally different than just checking if the string is empty.
From the linked documentation:
Checks if a String is whitespace, empty ("") or null.
StringUtils.isBlank(null) = true StringUtils.isBlank("") = true StringUtils.isBlank(" ") = true StringUtils.isBlank("bob") = false StringUtils.isBlank(" bob ") = false
For comparison StringUtils.isEmpty:
StringUtils.isEmpty(null) = true
StringUtils.isEmpty("") = true
StringUtils.isEmpty(" ") = false
StringUtils.isEmpty("bob") = false
StringUtils.isEmpty(" bob ") = false
Warning: In java.lang.String.isBlank() and java.lang.String.isEmpty() work the same except they don't return true for null.
java.lang.String.isBlank() (since Java 11)
java.lang.String.isEmpty()
StringUtils.isBlank() checks that each character of the string is a whitespace character (or that the string is empty or that it's null). This is totally different than just checking if the string is empty.
From the linked documentation:
Checks if a String is whitespace, empty ("") or null.
StringUtils.isBlank(null) = true StringUtils.isBlank("") = true StringUtils.isBlank(" ") = true StringUtils.isBlank("bob") = false StringUtils.isBlank(" bob ") = false
For comparison StringUtils.isEmpty:
StringUtils.isEmpty(null) = true
StringUtils.isEmpty("") = true
StringUtils.isEmpty(" ") = false
StringUtils.isEmpty("bob") = false
StringUtils.isEmpty(" bob ") = false
Warning: In java.lang.String.isBlank() and java.lang.String.isEmpty() work the same except they don't return true for null.
java.lang.String.isBlank() (since Java 11)
java.lang.String.isEmpty()
The accepted answer from @arshajii is totally correct. However just being more explicit by saying below,
StringUtils.isBlank()
StringUtils.isBlank(null) = true
StringUtils.isBlank("") = true
StringUtils.isBlank(" ") = true
StringUtils.isBlank("bob") = false
StringUtils.isBlank(" bob ") = false
StringUtils.isEmpty
StringUtils.isEmpty(null) = true
StringUtils.isEmpty("") = true
StringUtils.isEmpty(" ") = false
StringUtils.isEmpty("bob") = false
StringUtils.isEmpty(" bob ") = false
Useful method from Apache Commons:
org.apache.commons.lang.StringUtils.isBlank(String str)
https://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/StringUtils.html#isBlank(java.lang.String)
To detect if a string is null or empty, you can use the following without including any external dependencies on your project and still keeping your code simple/clean:
if(myString==null || myString.isEmpty()){
//do something
}
or if blank spaces need to be detected as well:
if(myString==null || myString.trim().isEmpty()){
//do something
}
you could easily wrap these into utility methods to be more concise since these are very common checks to make:
public final class StringUtils{
private StringUtils() { }
public static bool isNullOrEmpty(string s){
if(s==null || s.isEmpty()){
return true;
}
return false;
}
public static bool isNullOrWhiteSpace(string s){
if(s==null || s.trim().isEmpty()){
return true;
}
return false;
}
}
and then call these methods via:
if(StringUtils.isNullOrEmpty(myString)){...}
and
if(StringUtils.isNullOrWhiteSpace(myString)){...}
What about isEmpty() ?
if(str != null && !str.isEmpty())
Be sure to use the parts of && in this order, because java will not proceed to evaluate the second part if the first part of && fails, thus ensuring you will not get a null pointer exception from str.isEmpty() if str is null.
Beware, it's only available since Java SE 1.6. You have to check str.length() == 0 on previous versions.
To ignore whitespace as well:
if(str != null && !str.trim().isEmpty())
(since Java 11 str.trim().isEmpty() can be reduced to str.isBlank() which will also test for other Unicode white spaces)
Wrapped in a handy function:
public static boolean empty( final String s ) {
// Null-safe, short-circuit evaluation.
return s == null || s.trim().isEmpty();
}
Becomes:
if( !empty( str ) )
Use org.apache.commons.lang.StringUtils
I like to use Apache commons-lang for these kinds of things, and especially the StringUtils utility class:
import org.apache.commons.lang.StringUtils;
if (StringUtils.isNotBlank(str)) {
...
}
if (StringUtils.isBlank(str)) {
...
}