package Queue;

import java.util.ArrayDeque;

import java.util.Deque;

import java.util.stream.IntStream;

class QueueUsingStack {

public static void main(String[] args) {

System.out.println("implementation of queue using insertionStack");

int size = 5;

QueueImplementation<Integer> queueImplementation = new QueueImplementation<>(size);

queueImplementation.enqueue(2);

System.out.println(queueImplementation.dequeue());

IntStream.range(0, size).forEach(queueImplementation::enqueue);

IntStream.range(0, size - 1).forEach(i -> {

System.out.print(queueImplementation.dequeue() + ", ");

});

System.out.println("\n"+ queueImplementation.dequeue());

}

}

class QueueImplementation<E> {

int CAPACITY;

Deque<E> insertionStack;

Deque<E> removalStack;

QueueImplementation(int size) {

this.CAPACITY = size;

this.insertionStack = new ArrayDeque<>();

this.removalStack = new ArrayDeque<>();

}

public void enqueue(E e) {

if (this.insertionStack.size() == this.CAPACITY) {

throw new RuntimeException("queue is full, remove at least one element before inserting.");

}

this.insertionStack.push(e);

}

public E dequeue() {

if (this.insertionStack.isEmpty() && this.removalStack.isEmpty()) {

throw new RuntimeException("queue is empty, insert an element before retrieving.");

}

if (this.removalStack.isEmpty()) {

while (!this.insertionStack.isEmpty()) {

this.removalStack.push(this.insertionStack.pop());

}

}

return removalStack.pop();

}

}