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Java Collections - ArrayBlockingQueue.peek() Examples

Java Collections Java Java API 

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Class:

java.util.concurrent.ArrayBlockingQueue

java.lang.Objectjava.lang.Objectjava.util.AbstractCollectionjava.util.AbstractCollectionjava.util.CollectionCollectionjava.util.AbstractQueuejava.util.AbstractQueuejava.util.QueueQueuejava.util.concurrent.ArrayBlockingQueuejava.util.concurrent.ArrayBlockingQueuejava.util.concurrent.BlockingQueueBlockingQueuejava.io.SerializableSerializableLogicBig

Method:

E peek()

Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.


Examples


package com.logicbig.example.arrayblockingqueue;

import java.util.Arrays;
import java.util.concurrent.ArrayBlockingQueue;

public class PeekExample {

    public static void main(String... args) {
        ArrayBlockingQueue<Integer> q = new ArrayBlockingQueue<>(3, true,
                Arrays.asList(1, 2, 3));
        System.out.println("queue: " + q);
        Integer i = q.peek();
        System.out.println(i);
        i = q.peek();
        System.out.println(i);
    }
}

Output

queue: [1, 2, 3]
1
1




In case if Queue is empty this method will return null (element() method will throw NoSuchElementException): 

package com.logicbig.example.arrayblockingqueue;

import java.util.concurrent.ArrayBlockingQueue;

public class PeekExample2 {

    public static void main(String... args) {
        ArrayBlockingQueue<Integer> q = new ArrayBlockingQueue<>(3);
        System.out.println("queue: " + q);
        Integer i = q.peek();
        System.out.println(i);
    }
}

Output

queue: []
null

See Also