arrayqueue.java

this how we make stack and queue in java.

package stackqueue;

public class ArrayQueue {
	private int[] queue;
	private int currentSize;
	private int front;
	private int back;
	private static final int DEFAULT_CAPACITY = 10;
	private int increment(int x) {
		if(++x == queue.length)
			x = 0;
		return x;
	}
	private void doubleQueue() {
		int[] temp = new int[queue.length * 2];
		for(int i = 0; i < currentSize; i++, front = increment(front))
			temp[i] = queue[front];
		queue = temp;
		front = 0;
		back = currentSize - 1;
	}
	
	public ArrayQueue() {
		queue = new int[DEFAULT_CAPACITY];
		makeEmpty();
	}
	public boolean isEmpty() {
		return currentSize == 0;
	}
	public void enqueue(int num){
		if(currentSize == queue.length)
			doubleQueue();
		back = increment(back);
		queue[back] = num;
		currentSize++;
	}
	public int dequeue() throws UnderflowException {
		if(isEmpty())
			throw new UnderflowException("Array Queue dequeue");
		currentSize--;
		int value = queue[front];
		front = increment(front);
		return value;
	}
	public int getFront() throws UnderflowException {
		if(isEmpty())
			throw new UnderflowException("Array Queue getFront");
		return queue[front];
	}
	public void makeEmpty() {
		currentSize = 0;
		front = 0;
		back = -1;
	}
}