Data Structures and Algorithm

src/com/javadevjournal/MyQueue.java

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+package com.javadevjournal;
+
+class MyQueue {
+    private int[] array;
+    private int front;
+    private int rear;
+    private int capacity;
+    private int size;
+
+    MyQueue(int size) {
+        array = new int[size];
+        capacity = size;
+        front = 0;
+        rear = -1;
+        this.size = 0;
+    }
+
+    /**
+     * dequeue from queue
+     */
+    public void dequeue() {
+        if (isEmpty()) {
+            System.out.println("Can't dequeue, Queue is empty");
+            return;
+        }
+        System.out.println("Dequeue:" + array[front]);
+        front = (front + 1) % capacity;
+        size--;
+    }
+
+    /**
+     * enqueue an item to the queue
+     * @param item
+     */
+    public void enqueue(int item) {
+        if (isFull()) {
+            System.out.println("Can't enqueue, Queue is full");
+            return;
+        }
+        System.out.println("Enqueuing:" + item);
+        rear = (rear + 1) % capacity;
+        array[rear] = item;
+        size++;
+    }
+
+    /**
+     * @return the size of the queue
+     */
+    public int size() {
+        return size;
+    }
+
+    /**
+     * checks if queue is empty
+     * @return
+     */
+    public Boolean isEmpty() {
+        return (size() == 0);
+    }
+
+    /**
+     * check if queue is full
+     * @return
+     */
+    public Boolean isFull() {
+        return (size() == capacity);
+    }
+
+    /**
+     * main method
+     * @param args
+     */
+    public static void main(String[] args) {
+        MyQueue queue = new MyQueue(3);
+        queue.enqueue(1);
+        queue.enqueue(2);
+        queue.enqueue(3);
+        queue.enqueue(4);
+        queue.dequeue();
+        queue.dequeue();
+        queue.dequeue();
+        queue.dequeue();
+        System.out.println("The queue size is " + queue.size());
+        queue.enqueue(5);
+        System.out.println("The queue size is " + queue.size());
+        queue.dequeue();
+        System.out.println("The queue size is " + queue.size());
+    }
+}

src/com/javadevjournal/MyStack.java

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+package com.javadevjournal;
+
+class MyStack
+{
+    private int array[];
+    private int top;
+    private int capacity;
+
+    MyStack(int size)
+    {
+        array = new int[size];
+        capacity = size;
+        top = -1;
+    }
+
+    /**
+     *
+     * @param item
+     */
+    public void push(int item)
+    {
+        if (isFull())
+        {
+            System.out.println("Can't push the element, Stack is full");
+            return;
+        }
+        System.out.println("Pushing: " + item);
+        array[++top] = item;
+    }
+
+    /**
+     *
+     * @return
+     */
+    public int pop()
+    {
+        if (isEmpty()) {
+            System.out.println("Can't pop the element, Stack is empty");
+            return -1;
+        }
+        System.out.println("Popping top element:"+array[top]);
+        return array[top--];
+    }
+
+    /**
+     * returns the size of stack
+     * @return
+     */
+    public int size() {
+        return top + 1;
+    }
+
+    /**
+     * checks is stack is empty
+     * @return
+     */
+    public Boolean isEmpty() {
+        return size() == 0;
+    }
+
+    /**
+     * checks if stack is full
+     * @return
+     */
+    public Boolean isFull() {
+        return size() == capacity;
+    }
+
+    public static void main (String[] args) {
+        MyStack stack = new MyStack(3);
+        stack.push(1);
+        stack.push(2);
+        stack.push(3);
+        stack.push(4);
+        stack.pop();
+        stack.pop();
+        stack.pop();
+        stack.pop();
+        stack.push(5);
+        System.out.println("The stack size is " + stack.size());
+        stack.pop();
+        System.out.println("The stack size is " + stack.size());
+    }
+}