Deque contains() method in Java

The contains(E e) method of Deque Interface check for the presence of the element e in the Deque container. If the Deque contains one occurrence of the element, then it returns true else it returns false.

Syntax:

boolean contains(Object o)

Parameters: This method accepts a mandatory parameter o which is the element that needs to be tested if it is present in the Deque or not.



Return Value: The method returns True if the element is present in the Deque otherwise it returns False.

Exceptions: The function throws two exceptions as shown below:

  • ClassCastException – if the type of the specified element is incompatible with this deque. It is optional.
  • NullPointerException – if the specified element is null and this Deque does not permit null elements (optional). It is optional.

Below programs illustrate the contains() method in Java:

Program 1: With the help of LinkedList.

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java code to illustrate contains()
// method of Deque in Java
import java.util.*;
  
public class GFG {
    public static void main(String args[])
    {
        // Creating an empty Deque
        Deque<String> de_que = new LinkedList<String>();
  
        // Use add() method to add elements into the Queue
        de_que.add("Welcome");
        de_que.add("To");
        de_que.add("Geeks");
        de_que.add("4");
        de_que.add("Geeks");
  
        // Displaying the Deque
        System.out.println("Deque: " + de_que);
  
        // Check for "Geeks" in the deque
        System.out.println("Does the deque contains 'Geeks'? "
                           + de_que.contains("Geeks"));
  
        // Check for "4" in the deque
        System.out.println("Does the deque contains '4'? "
                           + de_que.contains("4"));
  
        // Check if the deque contains "No"
        System.out.println("Does the deque contains 'No'? "
                           + de_que.contains("No"));
    }
}

chevron_right


Output:

Deque: [Welcome, To, Geeks, 4, Geeks]
Does the deque contains 'Geeks'? true
Does the deque contains '4'? true
Does the deque contains 'No'? false

Program 2:

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java code to illustrate contains()
// method of Deque in Java
import java.util.*;
  
public class GFG {
    public static void main(String args[])
    {
        // Creating an empty Deque
        Deque<Integer> de_que = new LinkedList<Integer>();
  
        // Use add() method to add elements into the Queue
        de_que.add(10);
        de_que.add(15);
        de_que.add(30);
        de_que.add(20);
        de_que.add(5);
  
        // Displaying the Deque
        System.out.println("Deque: " + de_que);
  
        // Check for '15' in the Deque
        System.out.println("Does the Deque contains '15'? "
                           + de_que.contains(15));
  
        // Check for '2' in the Deque
        System.out.println("Does the Deque contains '2'? "
                           + de_que.contains(2));
  
        // Check if the Deque contains '10'
        System.out.println("Does the Deque contains '10'? "
                           + de_que.contains(10));
    }
}

chevron_right


Output:

Deque: [10, 15, 30, 20, 5]
Does the Deque contains '15'? true
Does the Deque contains '2'? false
Does the Deque contains '10'? true

Program 3: With the help of ArrayDeque.

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java code to illustrate contains()
// method of Deque in Java
import java.util.*;
  
public class GFG {
    public static void main(String args[])
    {
        // Creating an empty Deque
        Deque<Integer> de_que = new ArrayDeque<Integer>();
  
        // Use add() method to add elements into the Queue
        de_que.add(10);
        de_que.add(15);
        de_que.add(30);
        de_que.add(20);
        de_que.add(5);
  
        // Displaying the Deque
        System.out.println("Deque: " + de_que);
  
        // Check for '15' in the Deque
        System.out.println("Does the Deque contains '15'? "
                           + de_que.contains(15));
  
        // Check for '2' in the Deque
        System.out.println("Does the Deque contains '2'? "
                           + de_que.contains(2));
  
        // Check if the Deque contains '10'
        System.out.println("Does the Deque contains '10'? "
                           + de_que.contains(10));
    }
}

chevron_right


Output:

Deque: [10, 15, 30, 20, 5]
Does the Deque contains '15'? true
Does the Deque contains '2'? false
Does the Deque contains '10'? true

Program 4: With the help of ConcurrentLinkedDeque.

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java code to illustrate contains()
// method of Deque in Java
import java.util.*;
import java.util.concurrent.ConcurrentLinkedDeque;
  
public class GFG {
    public static void main(String args[])
    {
        // Creating an empty Deque
        Deque<Integer> de_que = new ConcurrentLinkedDeque<Integer>();
  
        // Use add() method to add elements into the Queue
        de_que.add(10);
        de_que.add(15);
        de_que.add(30);
        de_que.add(20);
        de_que.add(5);
  
        // Displaying the Deque
        System.out.println("Deque: " + de_que);
  
        // Check for '15' in the Deque
        System.out.println("Does the Deque contains '15'? "
                           + de_que.contains(15));
  
        // Check for '2' in the Deque
        System.out.println("Does the Deque contains '2'? "
                           + de_que.contains(2));
  
        // Check if the Deque contains '10'
        System.out.println("Does the Deque contains '10'? "
                           + de_que.contains(10));
    }
}

chevron_right


Output:

Deque: [10, 15, 30, 20, 5]
Does the Deque contains '15'? true
Does the Deque contains '2'? false
Does the Deque contains '10'? true

Program 5: With the help of LinkedBlockingDeque.

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java code to illustrate contains()
// method of Deque in Java
import java.util.*;
import java.util.concurrent.LinkedBlockingDeque;
  
public class GFG {
    public static void main(String args[])
    {
        // Creating an empty Deque
        Deque<Integer> de_que = new LinkedBlockingDeque<Integer>();
  
        // Use add() method to add elements into the Queue
        de_que.add(10);
        de_que.add(15);
        de_que.add(30);
        de_que.add(20);
        de_que.add(5);
  
        // Displaying the Deque
        System.out.println("Deque: " + de_que);
  
        // Check for '15' in the Deque
        System.out.println("Does the Deque contains '15'? "
                           + de_que.contains(15));
  
        // Check for '2' in the Deque
        System.out.println("Does the Deque contains '2'? "
                           + de_que.contains(2));
  
        // Check if the Deque contains '10'
        System.out.println("Does the Deque contains '10'? "
                           + de_que.contains(10));
    }
}

chevron_right


Output:

Deque: [10, 15, 30, 20, 5]
Does the Deque contains '15'? true
Does the Deque contains '2'? false
Does the Deque contains '10'? true

Note: The exceptions are compiler dependent, hence cannot be shown in the program.
Reference: https://docs.oracle.com/javase/8/docs/api/java/util/Deque.html#contains-java.lang.Object-



My Personal Notes arrow_drop_up

The function of education is to teach one to think intensively and to think critically

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.