Deque contains() method in Java
Last Updated :
21 Sep, 2018
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
// 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"));
}
}
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
// 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));
}
}
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
// 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));
}
}
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
// 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));
}
}
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
// 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));
}
}
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-