Java Collections checkedQueue() Method

The checkedQueue() is a method of Java Collections class which returns a dynamically typesafe view of the specified Queue. If an element inserted of the wrong type, it will result in an immediate ClassCastException.

Syntax

Following is the declaration of checkedQueue() method:

Parameter

Parameter	Description	Required/Optional
queue	It is the Queue for which a dynamically typesafe view is to be returned.	Required
type	It is the type of element that Queue is permitted to hold.	Required

Returns

The checkedQueue() method returns a dynamically typesafe view of the specified Queue.

Exceptions

ClassCastException

Compatibility Version

Java 1.8 and above

Example 1

import java.util.*;
public class CollectionsCheckedQueueExample1 {
	public static void main(String[] args) {
		//Create list       
	      Queue<String> queue = new PriorityQueue<String>();
	      queue.add("A");
	      queue.add("B");
	      queue.add("C");
	      queue.add("D");
	      //Create type safe view of the List          
	      System.out.println("Type safe view of the Queue is: "+Collections.checkedQueue(queue,String.class));
	      }
}

Test it Now

Output:

Type safe view of the Queue is: [A, B, C, D]

Example 2

import java.util.*;
public class CollectionsCheckedQueueExample2 {
	public static void main(String[] args) {
		 //Create list       
	      Queue<Integer> queue = new PriorityQueue<Integer>();
	      queue.add(55);
	      queue.add(66);
	      queue.add(77);
	      queue.add(77);
	      queue.add(88);
	      queue.add(66);
	      //Create type safe view of the List          
	      System.out.println("Type safe view of the Queue is: "+Collections.checkedQueue(queue,Integer.class));
	      }
}

Test it Now

Output:

Type safe view of the Queue is: [55, 66, 66, 77, 88, 77]

Example 3

import java.util.*;
public class CollectionsCheckedQueueExample3 {
	public static void main(String[] args) {
		Queue<Integer> queue = new PriorityQueue<>();
            queue = Collections.checkedQueue(queue, Integer.class);
            queue.offer(1);
            queue.offer(2);
            queue.offer(5);
            System.out.println("\n"+queue);
            Queue queue2 = queue;
            queue2.offer("Four");
            System.out.println(queue2);
	      }
}

Test it Now

Output:

[1, 2, 5]
Exception in thread "main" java.lang.ClassCastException: Attempt to insert class java.lang.String element into collection with element type class java.lang.Integer
	at java.base/java.util.Collections$CheckedCollection.typeCheck(Collections.java:3038)
	at java.base/java.util.Collections$CheckedQueue.offer(Collections.java:3188)
	at myPackage.CollectionCheckedQueueExample3.main(CollectionCheckedQueueExample3.java:12)

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