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.
// Java code to illustrate contains()// method of Deque in Javaimport 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")); }} |
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:
// Java code to illustrate contains()// method of Deque in Javaimport 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)); }} |
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.
// Java code to illustrate contains()// method of Deque in Javaimport 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)); }} |
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.
// Java code to illustrate contains()// method of Deque in Javaimport 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)); }} |
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.
// Java code to illustrate contains()// method of Deque in Javaimport 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)); }} |
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-
