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Java Collections - Collections.checkedQueue() Examples

[Last Updated: Dec 11, 2025]

Java Collections Java Java API 

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Class:

java.util.Collections

java.lang.Objectjava.lang.Objectjava.util.Collectionsjava.util.CollectionsLogicBig

Method:

public static <E> Queue<E> checkedQueue(Queue<E> queue,
                                        Class<E> type)

Returns a dynamically typesafe view of the specified Queue.


Examples


package com.logicbig.example.collections;

import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Queue;

public class CheckedQueueExample {

    public static void main(String... args) {
        Comparator comparator = (o1, o2) -> 1;
        Queue<Integer> queue = new PriorityQueue<>(comparator);
        queue.offer(1);
        queue.offer(2);
        System.out.println(queue);

        Queue queue2 = queue;
        queue2.offer("three");
        System.out.println(queue2);
    }
}

Output

[1, 2]
[1, 2, three]
JDK 25




Using checkedQueue: 

package com.logicbig.example.collections;

import java.util.Collections;
import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Queue;

public class CheckedQueueExample2 {

    public static void main(String... args) {
        Comparator comparator = (o1, o2) -> 1;
        Queue<Integer> queue = new PriorityQueue<>(comparator);
        queue = Collections.checkedQueue(queue, Integer.class);
        queue.offer(1);
        queue.offer(2);
        System.out.println(queue);

        Queue queue2 = queue;
        queue2.offer("three");
        System.out.println(queue2);
    }
}

Output

[1, 2]
java.lang.ClassCastException: Attempt to insert class java.lang.String element into collection with element type class java.lang.Integer
    at java.util.Collections$CheckedCollection.typeCheck (Collections.java:3455)
    at java.util.Collections$CheckedQueue.offer (Collections.java:3615)
    at com.logicbig.example.collections.CheckedQueueExample2.main (CheckedQueueExample2.java:25)
    at jdk.internal.reflect.DirectMethodHandleAccessor.invoke (DirectMethodHandleAccessor.java:104)
    at java.lang.reflect.Method.invoke (Method.java:565)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.executeMainMethod (AbstractExecJavaBase.java:402)
    at org.codehaus.mojo.exec.ExecJavaMojo.executeMainMethod (ExecJavaMojo.java:142)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.doExecClassLoader (AbstractExecJavaBase.java:377)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.lambda$execute$0 (AbstractExecJavaBase.java:287)
    at java.lang.Thread.run (Thread.java:1474)
JDK 25

See Also