The clear() of java.util.Collection interface is used to clear the Collection upon which it is called. This method does not take any parameter and does not returns any value.
Syntax:
Collection.clear()
Parameters: This method do not accept any parameter
Return Value: This method does not return any value.
Exceptions: This method throws following exceptions:
- UnsupportedOperationException: if the add operation is not supported by this collection
Below examples illustrate the Collection clear() method:
Example 1: Using LinkedList Class
// Java code to illustrate boolean clear() 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); // 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 ArrayDeque Class
// 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 ArrayList Class
// 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: https://docs.oracle.com/javase/9/docs/api/java/util/Collection.html#clear–