Java ArrayList clear() Method

The ArrayList.clear() method in Java is used to remove all elements from an ArrayList. This guide will cover the method's usage, explain how it works, and provide examples to demonstrate its functionality.

Table of Contents

1. Introduction
2. clear Method Syntax
3. Examples
   • Clearing an ArrayList
   • Verifying if the ArrayList is Empty
4. Conclusion

Introduction

The clear() method is a member of the ArrayList class in Java. It allows you to remove all elements from the ArrayList, effectively resetting it to an empty state. This method is particularly useful when you want to reuse an ArrayList without retaining its previous elements.

clear Method Syntax

The syntax for the clear method is as follows:

public void clear()

• The method does not take any parameters and does not return any value.

Examples

Clearing an ArrayList

The clear method can be used to remove all elements from an ArrayList.

Example

import java.util.ArrayList;

public class ClearExample {
    public static void main(String[] args) {
        ArrayList<String> list = new ArrayList<>();
        list.add("Apple");
        list.add("Banana");
        list.add("Orange");

        System.out.println("ArrayList before clear: " + list);

        // Clear the ArrayList
        list.clear();

        System.out.println("ArrayList after clear: " + list);
    }
}

Output:

ArrayList before clear: [Apple, Banana, Orange]
ArrayList after clear: []

Verifying if the ArrayList is Empty

After clearing an ArrayList, you can verify if it is empty using the isEmpty() method.

Example

import java.util.ArrayList;

public class ClearAndCheckExample {
    public static void main(String[] args) {
        ArrayList<String> list = new ArrayList<>();
        list.add("Apple");
        list.add("Banana");
        list.add("Orange");

        System.out.println("ArrayList before clear: " + list);

        // Clear the ArrayList
        list.clear();

        // Check if the ArrayList is empty
        boolean isEmpty = list.isEmpty();
        System.out.println("Is ArrayList empty after clear? " + isEmpty);
    }
}

Output:

ArrayList before clear: [Apple, Banana, Orange]
Is ArrayList empty after clear? true

Conclusion

The ArrayList.clear() method in Java is a simple and effective way to remove all elements from an ArrayList. By understanding how to use this method, you can efficiently manage the state of your collections in Java applications. Whether you are clearing the list to reuse it or to ensure it is empty, the clear method provides a straightforward solution for these tasks.