Add code

CONTRIBUTORS.md

@@ -1,3 +1,4 @@
 # Add yourself in this file if you are a contributor for Hacktoberfest 2018
 
 - Radu Stochitoiu
+- Aravind V. Nair ([@AravindVNair99](https://github.com/AravindVNair99)), Computer Science enthusiast mainly interested in web development and cybersecurity [Portfolio Website](https://aravindvnair99.firebaseapp.com), [Blog](https://aravindvnair1999.blogspot.com)

Java/algorithms/PasswordGenerator.java

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+// Generate random password of given length
+
+import java.util.Random;
+import java.util.Scanner;
+
+public class PasswordGenerator {
+	public static void main(String[] args) {
+		Scanner sc = new Scanner(System.in);
+		System.out.println("Enter the length of the password you require:\n");
+		System.out.println(generatePswd(sc.nextInt()));
+		sc.close();
+	}
+
+	static char[] generatePswd(int len) {
+		System.out.println("\nYour password is:\n");
+		String charsCaps = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+		String chars = "abcdefghijklmnopqrstuvwxyz";
+		String nums = "0123456789";
+		String symbols = "!@#$%^&*_=+-/€.?<>)";
+		String passSymbols = charsCaps + chars + nums + symbols;
+		Random rnd = new Random();
+		char[] password = new char[len];
+		int index = 0;
+		for (int i = 0; i < len; i++) {
+			password[i] = passSymbols.charAt(rnd.nextInt(passSymbols.length()));
+		}
+		return password;
+	}
+}

Java/algorithms/ReverseArrayUsingStack.java

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+//Reverse an array using stack
+
+import java.util.Scanner;
+import java.util.Stack;
+
+public class Main {
+	public static void main(String[] args) {
+		Scanner sc = new Scanner(System.in);
+		int n;
+		System.out.println("Enter the size of the array:");
+		n = sc.nextInt();
+		Stack<Integer> st = new Stack<Integer>();
+		int[] a = new int[n];
+		System.out.println("\nEnter the elements of the array:");
+		for (int i = 0; i < n; i++) {
+			a[i] = sc.nextInt();
+		}
+		for (int i = 0; i < n; i++) {
+			st.push(a[i]);
+		}
+		System.out.println("\nArray after reversing:");
+		for (int i = 0; i < n; i++) {
+			System.out.println(a[i] = st.pop());
+		}
+		sc.close();
+	}
+}

Java/data-structures/CircularQueueUsingArray.java

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+import java.util.Scanner;
+
+public class CircularQueueUsingArray {
+	public static void main(String[] args) {
+		Scanner input = new Scanner(System.in);
+		System.out.print("Enter total no of elements to be in the queue: ");
+		int maxSize = input.nextInt();
+		CircularQueue queue = new CircularQueue(maxSize);
+		int select;
+		int term = 0;
+		while (term == 0) {
+			System.out.print(
+					"\nOption:\tTo Do:\n1\tTo enqueue element.\n2\tTo dequeue element.\n3\tTo Display the Queue elements.\n4\tTo Exit the Program.\n\nEnter your option:- ");
+			select = input.nextInt();
+			switch (select) {
+			case 1: {
+				System.out.print("\nEnter element to insert in the queue: ");
+				int ele = input.nextInt();
+				queue.enqueue(ele);
+				break;
+			}
+			case 2: {
+				queue.dequeue();
+				break;
+			}
+			case 3: {
+				queue.display();
+				break;
+			}
+			case 4: {
+				term = 1;
+				System.out.println("\nSee you next time!");
+				input.close();
+				break;
+			}
+			default:
+				System.out.println("\nEnter a valid option.");
+			}
+		}
+	}
+}
+
+class CircularQueue {
+	int maxSize;
+	int rear;
+	int front;
+	int aQueue[];
+	{
+		rear = -1;
+		front = -1;
+	}
+
+	CircularQueue(int maxSize) {
+		this.maxSize = maxSize;
+		this.aQueue = new int[maxSize];
+	}
+
+	void enqueue(int item) {
+		if (((rear + 1) % maxSize) == front) {
+			System.out.println("\nQueue is full");
+		} else {
+			if (rear == front && front == -1) {
+				front += 1;
+			}
+			rear = (rear + 1) % maxSize;
+			aQueue[rear] = item;
+		}
+	}
+
+	void dequeue() {
+		if (rear == front && rear == -1) {
+			System.out.println("\nQueue is empty.");
+		} else {
+			int item = aQueue[front];
+			if (rear == front) {
+				rear = -1;
+				front = -1;
+			} else {
+				front = (front + 1) % maxSize;
+			}
+			System.out.println(item + " is deQueued from the Queue");
+		}
+	}
+
+	void display() {
+		int tempfront = front;
+		if (rear == front && rear == -1) {
+			System.out.println("\nQueue is Empty.");
+		} else {
+			System.out.println("\nThe contents of the queue are:- ");
+			for (int i = 0; i < maxSize; i++) {
+				if (tempfront != rear) {
+					System.out.println(aQueue[tempfront]);
+					tempfront = (tempfront + 1) % maxSize;
+				} else {
+					System.out.println(aQueue[rear]);
+					break;
+				}
+			}
+		}
+	}
+}