Collection clear() method in Java with Examples

29 Nov, 2018
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);    }}
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);    }}
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);    }}
ArrayList: [15, 20, 25]
The new ArrayList is: []

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