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Java Collections - ArrayDeque.peekFirst() Examples

Java Collections Java Java API

Class:

java.util.ArrayDeque

Method:

public E peekFirst()

Retrieves, but does not remove, the first element of this deque, or returns null if this deque is empty.

Examples

package com.logicbig.example.arraydeque;

import java.util.ArrayDeque;
import java.util.List;

public class PeekFirstExample {

    public static void main(String... args) {
        ArrayDeque<Integer> ad = new ArrayDeque<>(List.of(3, 8, 5, 7));
        Integer element = ad.peekFirst();
        System.out.println(element);
        System.out.println(ad);
    }
}

Output

3
[3, 8, 5, 7]

package com.logicbig.example.arraydeque;

import java.util.ArrayDeque;
import java.util.List;

public class PeekFirstExample2 {

    public static void main(String... args) {
        ArrayDeque<Integer> ad = new ArrayDeque<>();
        Integer element = ad.peekFirst();
        System.out.println(ad);
        System.out.println(element);
    }
}

Output

[]
null

See Also