Queue Implementation In JAVA

Queue Implementation In JAVA

import java.io.*;
class Queue
{
    int size = 10;     
    int que[];
    int rear, front;     
     
    Queue()
    {
        que = new int[size];
        rear = -1;
        front = 0;
    }
 
    void insert(int x)
    { 
        if(rear==size)
            System.out.println("Queue is full");
        else if(rear == -1)     
        {
            que[++rear] = x;
            front++;
        }
        else
            que[++rear] = x;
    }
 
    void delete()
    {
        if(front == -1)
            System.out.println("Queue is empty");
        else if(rear == front)
            rear = front = -1;
        else
            front++;
    }
 
    void display()
    {     
        for(int i=front; i<=rear;i++)
            System.out.print("\t"+que[i]);
 
        System.out.println("");
    }
}
 
class QueueImpl
{
    public static void main(String args[])
    {
        DataInputStream in = new DataInputStream(System.in);
        Queue q= new Queue();
        q.insert(6);
        q.insert(13);         
        q.insert(2);
        q.insert(19);
        q.insert(10);
        q.insert(7);
         
 
        q.delete();
        q.delete();
        System.out.println("Initial Queue");
        q.display();
         
        int ch = 4;
        do
        {
        System.out.println("What operation you wan to perform?:");
        System.out.println("1. Insert an element in queue");
        System.out.println("2. Delete an element from queue");
        System.out.println("3. Display queue");
        System.out.println("4. Quit"); 
         
         
 
        try {
            ch= Integer.parseInt(in.readLine());}
        catch(Exception e) { }
        int x = 0;
        switch(ch)
        {     
            case 1:
                System.out.println("Enter the element");
                try {
                    x= Integer.parseInt(in.readLine());}
                catch(Exception e) { }
                 
                q.insert(x);
                System.out.println("Now the Queue is:");
                q.display();
                break;
 
            case 2:
                q.delete();
                System.out.println("Element deleted");
                System.out.println("Now the Queue is:");
                q.display();
                break;
 
            case 3:
                q.display();
                break;
     
            default:
                System.out.println("Wrong choice");
        }
        } while (ch!=4);
    }
}
 
------------------------------------Output----------------------------------
-----------------------------------------------------------------------------
Initial Queue
        19      10      7
What operation you wan to perform?:
1. Insert an element in queue
2. Delete an element from queue
3. Display queue
4. Quit
1
Enter the element
23
Now the Queue is:
        19      10      7       23
What operation you wan to perform?:
1. Insert an element in queue
2. Delete an element from queue
3. Display queue
4. Quit
1
Enter the element
67
Now the Queue is:
        19      10      7       23      67
What operation you wan to perform?:
1. Insert an element in queue
2. Delete an element from queue
3. Display queue
4. Quit
2
Element deleted
Now the Queue is:
        10      7       23      67
What operation you wan to perform?:
1. Insert an element in queue
2. Delete an element from queue
3. Display queue
4. Quit
1
Enter the element
12
Now the Queue is:
        10      7       23      67      12
What operation you wan to perform?:
1. Insert an element in queue
2. Delete an element from queue
3. Display queue
4. Quit
4
Wrong choice

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