// Queue.java

// Circular-array implementation

import java.io.*;

public class Misc_Queue {

static final int MAX_QUEUE = 10;

int front;

int rear;

Object [] data;

public Misc_Queue()

{

front = 0;

rear = 0;

data = new Object[MAX_QUEUE];

}

static int

next(int x) /* Private function */

{

return (x + 1) % MAX_QUEUE;

}

boolean queueIsEmpty()

{

return (rear == front);

}

boolean queueIsFull()

{

return (next(rear) == front);

}

boolean QueueAdd(Object NewItem)

{

if (queueIsFull())

return false;

else {

data[rear] = NewItem;

rear = next(rear);

return true;

}

}

public Object QueueRemove()

{

if (queueIsEmpty())

return null;

else

{

Object retval = data[front];

front = next(front);

return retval;

}

}

public Object GetQueueFront()

{

if (queueIsEmpty())

return null;

else

return data[front];

}

public void DisplayQueue()

{

if (queueIsEmpty())

System.out.println("Empty Queue\n");

else

{

System.out.println("\nQueue\n-----");

for (int i=front;i!=rear;i=next(i)) {

System.out.println(data[i]);

}

System.out.println(" ");

}

}

public static void main(String args[])

{

System.out.println("Start Queue\n-----------\n");

Misc_Queue example = new Misc_Queue();

//String str = new String("one");

//Leads to the same result as the statement above.

//Statement above was probably required due to some JBook-java limitation.

String one = "one";

System.out.print("Add: ");

if (example.QueueAdd(one))

System.out.println(one);

else

System.out.println("Insert Failed");

example.DisplayQueue();

String two = "two";

System.out.print("Add: ");

if (example.QueueAdd(two))

System.out.println(two);

else

System.out.println("Insert Failed");

example.DisplayQueue();

System.out.print("Remove: ");

Object result = example.QueueRemove();

if (result == null)

System.out.println("Failed");

else

System.out.println(result);

example.DisplayQueue();

System.out.print("Remove: ");

result = example.QueueRemove();

if (result == null)

System.out.println("Failed");

else

System.out.println(result);

example.DisplayQueue();

System.out.print("Remove: ");

result = example.QueueRemove();

if (result == null)

System.out.println("Failed");

else

System.out.println(result);

example.DisplayQueue();

for (int i=0;i<20;i++)

{

String str = "loop";

System.out.print("Add: ");

if (example.QueueAdd(str))

System.out.println(str);

else

System.out.println("Insert Failed");

}

example.DisplayQueue();

for (int i=0;i<20;i++)

{

System.out.print("Remove: ");

result = example.QueueRemove();

if (result == null)

System.out.println("Failed");

else

System.out.println(result);

}

example.DisplayQueue();

}

}

//Start Queue

//-----------

//

//Add: one

//

//Queue

//-----

//one

//

//Add: two

//

//Queue

//-----

//one

//two

//

//Remove: one

//

//Queue

//-----

//two

//

//Remove: two

//Empty Queue

//

//Remove: Failed

//Empty Queue

//

//Add: loop

//Add: loop

//Add: loop

//Add: loop

//Add: loop

//Add: loop

//Add: loop

//Add: loop

//Add: loop

//Add: Insert Failed

//Add: Insert Failed

//Add: Insert Failed

//Add: Insert Failed

//Add: Insert Failed

//Add: Insert Failed

//Add: Insert Failed

//Add: Insert Failed

//Add: Insert Failed

//Add: Insert Failed

//Add: Insert Failed

//

//Queue

//-----

//loop

//loop

//loop

//loop

//loop

//loop

//loop

//loop

//loop

//

//Remove: loop

//Remove: loop

//Remove: loop

//Remove: loop

//Remove: loop

//Remove: loop

//Remove: loop

//Remove: loop

//Remove: loop

//Remove: Failed

//Remove: Failed

//Remove: Failed

//Remove: Failed

//Remove: Failed

//Remove: Failed

//Remove: Failed

//Remove: Failed

//Remove: Failed

//Remove: Failed

//Remove: Failed

//Empty Queue