Queue implementation using Linked List in Java

import java.io.*;
class Node
{
public int item;
public Node next;
public Node(int val)
{
item = val;
}
}
class LinkedList
{
private Node front,rear;
public LinkedList()
{
front = null;
rear = null;
}
public void insert(int val)
{
Node newNode = new Node(val);
if (front == null) {
            front = rear = newNode;
        }
else {
            rear.next = newNode;
rear = newNode;
}
}
public int delete()
{
if(front==null)
{
System.out.println("Queue is Empty");
return 0;
}
else
{
int temp = front.item;
            front = front.next;
            return temp;
}
}
public void display()
{
if(front==null)
{
System.out.println("Queue is Empty");
}
else
{
System.out.println("Elements in the Queue");
Node current = front;
while(current != null)
{
System.out.println("[" + current.item + "] ");
current = current.next;
}
System.out.println("");
}
}

}

Stack implementation using Linked List in Java

import java.io.*;
class Node
{
public int item;
public Node next;
public Node(int val)
{
item = val;
}
}
class LinkedList
{
private Node first;
public LinkedList()
{
first = null;
}
public void push(int val)
{
Node newNode = new Node(val);
newNode.next = first;
first = newNode;
}
public int pop()
{
if(first==null)
{
System.out.println("Stack is Empty");
return 0;
}
else
{
int temp = first.item;
first = first.next;
return temp;
}
}
public void display()
{
if(first==null)
{
System.out.println("Stack is Empty");
}
else
{
System.out.println("Elements from top to bottom");
Node current = first;
while(current != null)
{
System.out.println("[" + current.item + "] ");
current = current.next;
}
System.out.println("");
}
}

}

Queue implementation using Array in Java

import java.io.*;
class Aray
{
private int a[];
public int c=0,i,front,rear;
public Aray()
{
a=new int[5];
front=0;
rear=-1;
}
public void insert(int val)
{
if(c<=4)
{
rear=(rear+1)%5;
a[rear]=val;
c++;
}
else
System.out.println("Queue is full");
}
public int delete()
{
if(c==0)
{
System.out.println("Queue is Empty");
return 0;
}
else
{
int temp = a[front];
front=(front+1)%5;
c--;
return temp;
}
}
public void display()
{
if(c==0)
{
System.out.println("Queue is Empty");
}
else
{
System.out.println("Elements from front to rear");
int m=0;
for(i=front;m<c;i++,m++)
{
if(i>4)
i=i%5;
System.out.println(a[i]);
}
}
}

}

Stack implementation using Array in Java

import java.io.*;
class Aray
{
private int a[];
public int t=-1,i;
public Aray()
{
a=new int[5];
}
public void push(int val)
{
if(t<4)
{
t++;
a[t]=val;
}
else
System.out.println("Stack is full");
}
public int pop()
{
if(t==-1)
{
System.out.println("Stack is Empty");
return 0;
}
else
{
int temp = a[t];
t--;
return temp;
}
}
public void display()
{
if(t==-1)
{
System.out.println("Stack is Empty");
}
else
{
System.out.println("Elements from top to bottom");
for(i=t;i>-1;i--)
System.out.println(a[i]);
}
}

}