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 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" ));
}
} |
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 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 ));
}
} |
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 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 ));
}
} |
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 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 ));
}
} |
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 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 ));
}
} |
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-