/*
implementation of queues using arrays
creating queue of Object - Integer
*/
import java.io.*;
class
MyQueueException extends Exception
{
MyQueueException(String str)
{
super("You Got an Exception :
\n"+str);
}
}
class MyQueue
{
private int head,tail,size;
private Object arr[];
MyQueue(int size)
{
head=tail=-1;
this.size=size;
arr=new Object[size];
}
public void enqueue(Object element)throws
MyQueueException
{
if(isFull())
throw new
MyQueueException("OVERFLOW !!!");
else
{
if(tail==-1)
head=tail=0;
else
tail++;
if(tail==size)
tail=0;
arr[tail]=element;
}
}
public Object dequeue()throws
MyQueueException
{
if(isEmpty())
throw new
MyQueueException("UNDERFLOW !!!");
else
{
if(head==tail) // if there is
only a single element in the queue
{
int tmp=tail;
head=tail=-1;
return arr[tmp];
}
head++;
if(head==size) // if the element
to be deleted is the last element of the array
{
head=0;
return arr[size-1];
}
return arr[head-1];
}
}
public Object peek()throws MyQueueException
{
if(isEmpty())
throw new
MyQueueException("UNDERFLOW !!!");
else
return arr[head];
}
public boolean isEmpty()
{
if(head==-1&&tail==-1)
return true;
return false;
}
public boolean isFull()
{
if((head==0 &&
tail==size-1)||(tail+1==head))
return true;
return false;
}
public int getSize()
{
return size;
}
public int getCurrentSize()
{
return
(getHead()<getTail()?getTail()-getHead()+1:getSize()-(getTail()-getHead()+1));
}
public int getHead()
{
return head;
}
public int getTail()
{
return tail;
}
}
class Main
{
public static void main(String args[])
throws IOException
{
BufferedReader br=new
BufferedReader(new InputStreamReader(System.in));
System.out.print("Enter the size
of the array : ");
int
n=Integer.parseInt(br.readLine());
MyQueue queue=new MyQueue(n);
while(true)
{
System.out.println("___________________________________\n");
System.out.println("You
have the following choices : \n");
System.out.println("1.
INSERT");
System.out.println("2.
DELETE");
System.out.println("3. PEEK");
System.out.println("4. get
size of Queue");
System.out.println("5.
Check whether the Queue is empty or not...");
System.out.println("6.
EXIT\n");
System.out.print("Enter
your choice : ");
int
ch=Integer.parseInt(br.readLine());
switch(ch)
{
case 1:
System.out.print("Enter
the number that you want to insert : ");
int
element=Integer.parseInt(br.readLine());
try
{
queue.enqueue(new
Integer(element));
System.out.println("Element
inserted successfully...");
}
catch(MyQueueException
e){System.out.println(e.getMessage());}
break;
case 2:
try
{
System.out.println(queue.dequeue()+"
deleted successfully...");
}
catch(MyQueueException
e){System.out.println(e.getMessage());}
break;
case 3:
try
{
System.out.println("the
head of the stack is : "+queue.peek());
}
catch(MyQueueException
e){System.out.println(e.getMessage());}
break;
case 4:
System.out.println("The
Maximum size of your queue is : "+queue.getSize());
System.out.println("The
current size of your queue is : "+queue.getCurrentSize());
break;
case 5:
System.out.println("Is
your queue Empty ? "+queue.isEmpty());
break;
case 6:
System.exit(0);
default:
System.out.println("wrong
choice entered...\nPlease enter a valid choice...");
}
}
}
}
