implement queue using linked list in java
Java program for implement queue using linked list. Here problem description and explanation.
/*
Java Program for
Implement queue using linked list
*/
// Create Q node
class QNode
{
public int data;
public QNode next;
QNode(int value)
{
this.data = value;
this.next = null;
}
}
public class MyQueue
{
public QNode head;
public QNode tail;
public int count;
public MyQueue()
{
this.head = null;
this.tail = null;
this.count = 0;
}
public int size()
{
return this.count;
}
public boolean isEmpty()
{
return this.count == 0;
}
// Add new node of queue
public void enqueue(int value)
{
// Create a new node
QNode node = new QNode(value);
if (this.head == null)
{
// Add first element into queue
this.head = node;
}
else
{
// Add node at the end using tail
this.tail.next = node;
}
this.count++;
this.tail = node;
}
// Delete a element into queue
int dequeue()
{
if (this.head == null)
{
System.out.println("Empty Queue");
return -1;
}
// Pointer variable which are storing
// the address of deleted node
QNode temp = this.head;
// Visit next node
this.head = head.next;
this.count--;
if (this.head == null)
{
// When deleting a last node of linked list
this.tail = null;
}
return temp.data;
}
// Get front node
public int peek()
{
if (this.head == null)
{
System.out.println("Empty Queue");
return -1;
}
return this.head.data;
}
public static void main(String[] args)
{
MyQueue task = new MyQueue();
// Initially number of element
System.out.println("isEmpty : " + task.isEmpty());
// Add element into queue
task.enqueue(10);
task.enqueue(20);
task.enqueue(30);
task.enqueue(40);
task.enqueue(50);
// Test other function
System.out.println("size : " + task.size());
System.out.println("peek : " + task.peek());
System.out.println("dequeue : " + task.dequeue());
System.out.println("size : " + task.size());
System.out.println("peek : " + task.peek());
System.out.println("isEmpty : " + task.isEmpty());
}
}

Output
isEmpty : true
size : 5
peek : 10
dequeue : 10
size : 4
peek : 20
isEmpty : false
Please share your knowledge to improve code and content standard. Also submit your doubts, and test case. We improve by your feedback. We will try to resolve your query as soon as possible.
New Comment