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–
