Collection clear() method in Java with Examples

The collection clear() method of  Java Collection Interface clears the Collection upon which it is called. After this method is called, the collection will be empty as it removes all the elements from the collection.

This method does not take any parameter and does not return any value.

Example:

Java

// Java program to demonstrate the
// usage of clear() method in ArrayList
import java.util.ArrayList;
import java.util.Arrays;

public class ClearMethodExample {
    public static void main(String[] args) {
        // Create an ArrayList and initialize it with some elements
        ArrayList<String> list = new ArrayList<>(Arrays.asList("1", "2", "3", "4"));

        // Display the list before clearing
        System.out.println("List before clearing: " + list);

        // Clear the list
        list.clear();

        // Display the list after clearing
        System.out.println("List after clearing: " + list);
    }
}

Output:

List before clearing: [1, 2, 3, 4]
List after clearing: []

Syntax

Collection.clear()

Parameters:

• This method does not accept any parameter

Returns:

• This method does not return any value.

Exceptions:

• UnsupportedOperationException: if the add operation is not supported by this collection

Collection clear() Method Examples

Let’s see some examples of how to use the collection clear() method in Java.

Example 1:

How to remove all elements from a collection using collection clear() Method

Java

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

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

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

        // 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);

        // Clearing the LinkedList
        list.clear();

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

Output

The list is: [Geeks, for, Geeks]
The new List is: []

Example 2:

Using the clear() method on ArrayDeque to remove its elements.

Java

// Java code to illustrate clear() 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);

        // Clearing the ArrayDeque
        de_que.clear();

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

Output

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]
The new ArrayDeque is: []

Example 3:

Using the clear() method on ArrayList

Java

// Java code to illustrate clear() 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);

        // Clearing the ArrayList
        arrlist.clear();

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

Output

ArrayList: [15, 20, 25]
The new ArrayList is: []

Reference: Official Oracle Documents

Whether you are a beginner starting Java programming or an experienced looking to brush up on your Java skills, this tutorial will provide you with a deep understanding of the collection clear function and its uses in Java.

The clear method in Java is a fundamental function for collection manipulation. With this guide, you can easily remove all elements of a collection using the clear function.

Read More Collection Methods