Java-2/DataStructures/Queues/Queues.java at master · yyfullstack/Java-2 · GitHub

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/**

* This implements Queues by using the class Queue.

* <p>

* A queue data structure functions the same as a real world queue.

* The elements that are added first are the first to be removed.

* New elements are added to the back/rear of the queue.

* @author Unknown

class Queue {

/**

* Max size of the queue

private int maxSize;

/**

* The array representing the queue

private int[] queueArray;

/**

* Front of the queue

private int front;

/**

* Rear of the queue

private int rear;

/**

* How many items are in the queue

private int nItems;

/**

* Constructor

* @param size Size of the new queue

public Queue(int size) {

maxSize = size;

queueArray = new int[size];

front = 0;

rear = -1;

nItems = 0;

}

/**

* Inserts an element at the rear of the queue

* @param x element to be added

* @return True if the element was added successfully

public boolean insert(int x) {

if (isFull())

return false;

if (rear == maxSize - 1) // If the back of the queue is the end of the array wrap around to the front

rear = -1;

rear++;

queueArray[rear] = x;

nItems++;

return true;

}

/**

* Remove an element from the front of the queue

* @return the new front of the queue

public int remove() { // Remove an element from the front of the queue

if (isEmpty()) {

System.out.println("Queue is empty");

return -1;

}

int temp = queueArray[front];

front++;

if (front == maxSize) //Dealing with wrap-around again

front = 0;

nItems--;

return temp;

}

/**

* Checks what's at the front of the queue

* @return element at the front of the queue

public int peekFront() {

return queueArray[front];

}

/**

* Checks what's at the rear of the queue

* @return element at the rear of the queue

public int peekRear() {

return queueArray[rear];

}

/**

* Returns true if the queue is empty

* @return true if the queue is empty

public boolean isEmpty() {

return (nItems == 0);

}

/**

* Returns true if the queue is full

* @return true if the queue is full

public boolean isFull() {

return (nItems == maxSize);

}

/**

* Returns the number of elements in the queue

* @return number of elements in the queue

public int getSize() {

return nItems;

}

/**

* This class is the example for the Queue class

* @author Unknown

public class Queues {

/**

* Main method

* @param args Command line arguments

public static void main(String args[]) {

Queue myQueue = new Queue(4);

myQueue.insert(10);

myQueue.insert(2);

myQueue.insert(5);

myQueue.insert(3);

// [10(front), 2, 5, 3(rear)]

System.out.println(myQueue.isFull()); // Will print true

myQueue.remove(); // Will make 2 the new front, making 10 no longer part of the queue

// [10, 2(front), 5, 3(rear)]

myQueue.insert(7); // Insert 7 at the rear which will be index 0 because of wrap around

// [7(rear), 2(front), 5, 3]

System.out.println(myQueue.peekFront()); // Will print 2

System.out.println(myQueue.peekRear()); // Will print 7

}

Java-2/DataStructures/Queues/Queues.java at master · yyfullstack/Java-2 · GitHub

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