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 to check if the collection is empty or null in Java.
Let's create a standard utility method to check if the collection is empty or null in Java.
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 < String > list = new ArrayList < String > ();
list.add("ABC");
System.out.println(isNotEmptyOrNull(list));
List < String > list1 = new LinkedList < > ();
list1.add("ABC");
System.out.println(isNotEmptyOrNull(list1));
Set < String > 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
true
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