Saturday, August 13, 2011

Queue using array in Java + Complete Program Source Code to Implement a Queue


Queue is an a Linear Data Structure which follows a FIFO(First in First Out) approach.There are two operations for a Queue
a)Enqueue -Insert an Element to the Queue
b)DeQueue -Remove an Element from the Queue

The Element Inserted First is Removed first from the Queue.A Queue has two main Postions
a)Rear- The Position/Element at the End of the Queue
b)Front-The Front most Element/Position of the Queue
In a Queue elements are Enqueued to the Rear and DeQueued from the Front.
The Program given below shows the Implementation a Queue un Java using an Array.

 import java.io.*;  
 import java.lang.*;  
 class clrqueue  
 {  
  DataInputStream get=new DataInputStream(System.in);  
  int a[];  
  int i,front=0,rear=0,n,item,count=0;  
  void getdata()  
  {  
  try  
   {  
   System.out.println("Enter the limit");  
   n=Integer.parseInt(get.readLine());  
   a=new int[n];  
   }   
  catch(Exception e)  
   {  
   System.out.println(e.getMessage());  
   }  
  }  
  void enqueue()  
  {  
   try  
   {  
   if(count<n)  
    {  
    System.out.println("Enter the element to be added:");  
    item=Integer.parseInt(get.readLine());  
    a[rear]=item;  
     rear++;  
    count++;  
    }  
   else  
    System.out.println("QUEUE IS FULL");  
   }  
  catch(Exception e)  
   {  
   System.out.println(e.getMessage());  
   }  
  }  
  void dequeue()  
  {  
   if(count!=0)  
    {  
    System.out.println("The item deleted is:"+a[front]);  
    front++;  
    count--;  
    }  
   else  
    System.out.println("QUEUE IS EMPTY");  
  if(rear==n)  
   rear=0;  
  }  
  void display()  
  {  
   int m=0;  
   if(count==0)  
   System.out.println("QUEUE IS EMPTY");  
   else  
   {  
   for(i=front;m<count;i++,m++)  
   System.out.println(" "+a[i]);  
   }  
  }  
 }  
 class Myqueue  
 {  
  public static void main(String arg[])  
  {  
  DataInputStream get=new DataInputStream(System.in);  
  int ch;  
  clrqueue obj=new clrqueue();  
  obj.getdata();  
  try  
  {  
   do  
   {  
   System.out.println(" 1.Enqueue  2.Dequeue  3.Display  4.Exit");  
   System.out.println("Enter the choice");  
   ch=Integer.parseInt(get.readLine());  
   switch (ch)  
   {  
   case 1:  
       obj.enqueue();  
      break;  
   case 2:  
      obj.dequeue();  
      break;  
   case 3:  
      obj.display();  
      break;  
   }  
   }  
   while(ch!=4);  
  }  
  catch(Exception e)  
  {  
  System.out.println(e.getMessage());  
  }  
  }  
 }  

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