In this short article, we will discuss how to check if the collection is empty or null in Java.
Let's create a standard utility method tocheck if the collection is empty or null in Java.
Let's create a standard utility method tocheck if the collection is empty or null in Java.
Learn Java collections framework in-depth atJava Collections Framework in Depth
Check if Collection is Empty or Null in Java - Utility Methods
- isEmptyOrNull[Collection collection] - Return true if the supplied Collection is null or empty. Otherwise, return false.
- isNotEmptyOrNull[Collection collection] - Return true if the supplied Collection is not null or not empty. Otherwise, return false.
1. isEmptyOrNull[Collection collection]
Return true if the supplied Collection is null or empty. Otherwise, return false.
public static boolean isEmptyOrNull[Collection collection] {
return [collection == null || collection.isEmpty[]];
}
2. isNotEmptyOrNull[Collection collection]
Return true if the supplied Collection is not null or not empty. Otherwise, return false.
public static boolean isNotEmptyOrNull[Collection collection] {
return !isEmptyOrNull[collection];
}
Complete Example
Here is a complete example to test the above utility methods
package net.javaguides.lang;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
public class CollectionNullOrEmptyExample {
public static void main[String[] args] {
// return true if collection is null or empty
System.out.println[isEmptyOrNull[null]];
System.out.println[isEmptyOrNull[new ArrayList < > []]];
System.out.println[isEmptyOrNull[new LinkedList < > []]];
System.out.println[isEmptyOrNull[new HashSet < > []]];
// return false if collection is not empty or null
System.out.println[isNotEmptyOrNull[new ArrayList < > []]];
System.out.println[isNotEmptyOrNull[new LinkedList < > []]];
System.out.println[isNotEmptyOrNull[new HashSet < > []]];
// return false if collection is not empty or null
List list = new ArrayList < String > [];
list.add["ABC"];
System.out.println[isNotEmptyOrNull[list]];
List list1 = new LinkedList < > [];
list1.add["ABC"];
System.out.println[isNotEmptyOrNull[list1]];
Set set = new HashSet < String > [];
set.add["ABC"];
System.out.println[isNotEmptyOrNull[set]];
}
public static boolean isEmptyOrNull[Collection collection] {
return [collection == null || collection.isEmpty[]];
}
public static boolean isNotEmptyOrNull[Collection collection] {
return !isEmptyOrNull[collection];
}
}
Output:
true
true
true
true
false
false
false
true
true
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