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Collection clear() method in Java with Examples

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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–


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Last Updated : 29 Nov, 2018
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