What are some examples of queue and stack implementations in Java?

Can you explain what a queue and a stack are in Java?

Sure! A queue is a data structure that follows the First In First Out (FIFO) principle, while a stack follows Last In First Out (LIFO).

Can you give me a simple example of how to implement a queue in Java?

Absolutely! Here's a basic implementation of a queue using an array:

class Queue {
    private int front, rear, capacity;
    private int[] queue;

    public Queue(int size) {
        capacity = size;
        front = 0;
        rear = -1;
        queue = new int[capacity];
    }

    public void enqueue(int item) {
        if (rear == capacity - 1) {
            System.out.println("Queue is full!");
            return;
        }
        queue[++rear] = item;
    }

    public int dequeue() {
        if (front > rear) {
            System.out.println("Queue is empty!");
            return -1;
        }
        return queue[front++];
    }
}

What about a stack? Can you show me an example of that too?

Sure! Here's a simple stack implementation using an array:

class Stack {
    private int top;
    private int capacity;
    private int[] stack;

    public Stack(int size) {
        capacity = size;
        top = -1;
        stack = new int[capacity];
    }

    public void push(int item) {
        if (top == capacity - 1) {
            System.out.println("Stack is full!");
            return;
        }
        stack[++top] = item;
    }

    public int pop() {
        if (top == -1) {
            System.out.println("Stack is empty!");
            return -1;
        }
        return stack[top--];
    }
}