Collection isEmpty() method in Java with Examples

The isEmpty() of java.util.Collection interface is used to check if the Collection upon which it is called is empty or not. This method does not take any parameter and does not returns any value.

Syntax:

Collection.isEmpty()

Parameters: This method do not accept any parameter

Return Value: This method does not return any value.

Below examples illustrate the Collection isEmpty() method:

Example 1: Using LinkedList Class

// Java code to illustrate boolean isEmpty() method

import java.io.*;
import java.util.*;

public class GFG {
    public static void main(String args[])
    {

        // creating an empty LinkedList
        Collection<String> list = new LinkedList<String>();

        // use add() method to add elements in the list
        list.add("Geeks");
        list.add("for");
        list.add("Geeks");

        // Output the present list
        System.out.println("The list is: " + list);

        // Check if list is empty
        // using isEmpty() method
        System.out.println("Is the LinkedList empty: "
                           + list.isEmpty());

        // Clearing the LinkedList
        list.clear();

        // printing the new list
        System.out.println("The new List is: " + list);

        // Check if list is empty
        // using isEmpty() method
        System.out.println("Is the LinkedList empty: "
                           + list.isEmpty());
    }
}

Output:

The list is: [Geeks, for, Geeks]
Is the LinkedList empty: false
The new List is: []
Is the LinkedList empty: true

Example 2: Using ArrayDeque Class

// Java code to illustrate isEmpty() method

import java.util.*;

public class ArrayDequeDemo {
    public static void main(String args[])
    {
        // Creating an empty ArrayDeque
        Collection<String> de_que = new ArrayDeque<String>();

        // Use add() method to add elements into the Deque
        de_que.add("Welcome");
        de_que.add("To");
        de_que.add("Geeks");
        de_que.add("4");
        de_que.add("Geeks");

        // Displaying the ArrayDeque
        System.out.println("ArrayDeque: " + de_que);

        // Check if ArrayDeque is empty
        // using isEmpty() method
        System.out.println("Is the ArrayDeque empty: "
                           + de_que.isEmpty());

        // Clearing the ArrayDeque
        de_que.clear();

        // printing the new ArrayDeque
        System.out.println("The new ArrayDeque is: "
                           + de_que);

        // Check if ArrayDeque is empty
        // using isEmpty() method
        System.out.println("Is the ArrayDeque empty: "
                           + de_que.isEmpty());
    }
}

Output:

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]
Is the ArrayDeque empty: false
The new ArrayDeque is: []
Is the ArrayDeque empty: true

Example 3: Using ArrayList Class

// Java code to illustrate isEmpty() method

import java.io.*;
import java.util.*;

public class ArrayListDemo {
    public static void main(String[] args)
    {

        // create an empty array list with an initial capacity
        Collection<Integer>
            arrlist = new ArrayList<Integer>(5);

        // use add() method to add elements in the list
        arrlist.add(15);
        arrlist.add(20);
        arrlist.add(25);

        // prints all the elements available in list
        System.out.println("ArrayList: " + arrlist);

        // Check if list is empty
        // using isEmpty() method
        System.out.println("Is the ArrayList empty: "
                           + arrlist.isEmpty());

        // Clearing the ArrayList
        arrlist.clear();

        // printing the new ArrayList
        System.out.println("The new ArrayList is: "
                           + arrlist);

        // Check if ArrayList is empty
        // using isEmpty() method
        System.out.println("Is the ArrayList empty: "
                           + arrlist.isEmpty());
    }
}

Output:

ArrayList: [15, 20, 25]
Is the ArrayList empty: false
The new ArrayList is: []
Is the ArrayList empty: true

Reference: https://docs.oracle.com/javase/9/docs/api/java/util/Collection.html#isEmpty–