import java.util.ArrayDeque;

class KW 
{
    public static void main(String[] args) 
    {
        //ArrayDeque class implements the Queue interface
        ArrayDeque<String> aq=new ArrayDeque<>();
        aq.add("Apple");
        aq.add("Orange");
        aq.add("Mango");
        aq.add("Grapes");
        aq.add("Cherry");
        aq.add("Apple");
        aq.add("Blueberry");
        
        for(String e:aq) 
        { 
            System.out.println(e); 
        }
        System.out.println("Size: "+aq.size());
    }
}

kodingwindow@kw:~$ javac KW.java
kodingwindow@kw:~$ java KW
Apple
Orange
Mango
Grapes
Cherry
Apple
Blueberry
Size: 7
kodingwindow@kw:~$ 

import java.util.ArrayDeque;

class KW 
{
    public static void main(String[] args) 
    {
        //ArrayDeque class implements the Queue interface
        ArrayDeque<String> aq=new ArrayDeque<>();
        aq.add("Apple");
        aq.add("Mango");
        aq.add("Grapes");
        aq.add("Cherry");
        aq.add("Apple");
        System.out.println(aq);
        if(aq.offerFirst("Orange")) //returns true on successful addition of an element
        {
            System.out.println("\nElement added at the first position of ArrayDeque");
            System.out.println(aq);
        }
        if(aq.offerLast("Blueberry"))
        {
            System.out.println("\nElement added at the last position of ArrayDeque");
            System.out.println(aq);
        }
        if(aq.offer("Pineapple"))
        {
            System.out.println("\nNew element added into the ArrayDeque");
            System.out.println(aq);
        }
    }
}

kodingwindow@kw:~$ javac KW.java
kodingwindow@kw:~$ java KW
[Apple, Orange, Mango, Grapes, Cherry, Apple, Blueberry]

New element added into the ArrayDeque
[Apple, Orange, Mango, Grapes, Cherry, Apple, Blueberry, Pineapple]
kodingwindow@kw:~$ 

import java.util.ArrayDeque;

class KW 
{
    public static void main(String[] args) 
    {
        //ArrayDeque class implements the Queue interface
        ArrayDeque<String> aq=new ArrayDeque<>();
        aq.add("Apple"); //First In First Out
        aq.add("Orange");
        aq.add("Mango");
        aq.add("Grapes");
        aq.add("Cherry");
        aq.add("Apple");
        aq.add("Blueberry"); //Last In Last Out
        System.out.println(aq);
        System.out.println("Head element: "+aq.element());
        
        aq.poll();
        System.out.println("\n"+aq);
        System.out.println("Peek element: "+aq.peek());
        
        aq.remove();
        System.out.println("\n"+aq);
        System.out.println("Peek element: "+aq.peek());
    }
}

kodingwindow@kw:~$ javac KW.java
kodingwindow@kw:~$ java KW
[Apple, Orange, Mango, Grapes, Cherry, Apple, Blueberry]
Head element: Apple

[Orange, Mango, Grapes, Cherry, Apple, Blueberry]
Peek element: Orange

[Mango, Grapes, Cherry, Apple, Blueberry]
Peek element: Mango
kodingwindow@kw:~$ 

import java.util.ArrayDeque;

class KW 
{
    public static void main(String[] args) 
    {
        //ArrayDeque class implements the Queue interface
        ArrayDeque<String> aq=new ArrayDeque<>();
        aq.add("Apple");
        aq.add("Mango");
        aq.add("Grapes");
        aq.add("Cherry");
        aq.add("Apple");
        System.out.println(aq);
        
        //aq.addFirst(null); //java.lang.NullPointerException

        aq.addFirst("Orange");
        aq.addLast("Blueberry");
        System.out.println(aq);
        
        aq.pollFirst();
        aq.pollLast();
        System.out.println(aq);
    }
}

kodingwindow@kw:~$ javac KW.java
kodingwindow@kw:~$ java KW
[Apple, Mango, Grapes, Cherry, Apple]
[Orange, Apple, Mango, Grapes, Cherry, Apple, Blueberry]
[Apple, Mango, Grapes, Cherry, Apple]
kodingwindow@kw:~$