Java Collection isEmpty() Method

The isEmpty() method of Java Collection Interface returns the boolean value 'true' if this collection contains no elements.

Syntax

Parameters

Return

The isEmpty () method returns the boolean value 'true' if this collection contains no elements else it returns false.

Example 1

import java.util.Collection;
import java.util.concurrent.ConcurrentLinkedQueue;
public class JavaCollectionIsEmptyExample1 {
    public static void main(String[] args) {
        Collection<Integer> collection = new ConcurrentLinkedQueue<Integer>();
        //returns true if the queue is empty
        if(collection.isEmpty()){
            System.out.println("The queue is empty.");
        }
        else{
            System.out.println("Elements are : "+collection);
        }
    }
}

Test it Now

Output:

The queue is empty.

Example 2

import java.util.Collection;
import java.util.concurrent.ConcurrentLinkedQueue;
public class JavaCollectionIsEmptyExample2 {
    public static void main(String[] args) {
        Collection<Integer> collection = new ConcurrentLinkedQueue<Integer>();
        //returns an exception for null element
        collection.add(null);
        //returns true if the queue is empty
        if(collection.isEmpty()){
            System.out.println("Add some elements because the queue is empty.");
        }
        else{
            System.out.println("Elements are : "+collection);
        }
    }
}

Test it Now

Output:

Exception in thread "main" java.lang.NullPointerException
	at java.util.concurrent.ConcurrentLinkedQueue.checkNotNull(ConcurrentLinkedQueue.java:920)
	at java.util.concurrent.ConcurrentLinkedQueue.offer(ConcurrentLinkedQueue.java:327)
	at java.util.concurrent.ConcurrentLinkedQueue.add(ConcurrentLinkedQueue.java:297)
	at com.javaTpoint.JavaCollectionIsEmptyExample2.main(JavaCollectionIsEmptyExample2.java:9)

Example 3

import java.util.Collection;
import java.util.concurrent.ConcurrentLinkedQueue;
public class JavaCollectionIsEmptyExample3 {
    public static void main(String[] args) {
        Collection<Integer> collection = new ConcurrentLinkedQueue<Integer>();
        for (int i = 1; i <= 5; i++){
            collection.add(i);
        }
        if(collection.isEmpty()){
            System.out.println("isEmpty() method returns "+collection.isEmpty());
            System.out.println("Add some elements because the queue is empty.");
        }
        else{
            System.out.println("isEmpty() method returns "+collection.isEmpty());
            System.out.println("Elements are : "+collection);
        }
    }
}

Test it Now

Output:

isEmpty() method returns false
Elements are : [1, 2, 3, 4, 5]

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Java Collection isEmpty() Method

Syntax

Parameters

Return

Example 1

Example 2

Example 3

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