GCD Greatest Common Divisor

package com.test;

import java.util.Scanner;

public class GCDExample {
 
 
    public static void main(String args[]){
     
        //Enter two number whose GCD needs to be calculated.      
        Scanner scanner = new Scanner(System.in);
        System.out.println("Please enter first number to find GCD");
        int number1 = scanner.nextInt();
        System.out.println("Please enter second number to find GCD");
        int number2 = scanner.nextInt();
      
        System.out.println("GCD of two numbers " + number1 +" and " 
                           + number2 +" is :" + findGCD(number1,number2));
      
      
    }

    /*
     * Java method to find GCD of two number using Euclid's method
     * @return GDC of two numbers in Java
     */
    private static int findGCD(int number1, int number2) {
        //base case
        if(number2 == 0){
            return number1;
        }
        return findGCD(number2, number1%number2);
    }
  
}

Check Duplicates in Java Array

package com.test;

import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class CheckAllDuplicatesInJavaArray {

    public static void main(String args[])  {
       
       String[] withDuplicates = new String[] {"one","two","three","one"};
        String[] withoutDuplicates = new String[] {"one","two","three"};
      
        System.out.println("Checking array with duplicate using brute force: " + bruteforce(withDuplicates));
        System.out.println("Checking array without any duplicate using brute force: " + bruteforce(withoutDuplicates));
      
        System.out.println("Checking array with duplicate using Set and List: " + checkDuplicateUsingSet(withDuplicates));
        System.out.println("Checking array without any duplicate using Set and List: " + checkDuplicateUsingSet(withoutDuplicates));

      
        System.out.println("Checking array with duplicate using Set and List: " + checkDuplicateUsingAdd(withDuplicates));
        System.out.println("Checking array without any duplicate using Set and List: " + checkDuplicateUsingAdd(withoutDuplicates));

      
    }
  
    /*
     * brute force way of checking if array contains duplicates in Java
     * comparing each elements to all other elements of array
     * complexity on order of O(n^2) not advised in production
     */
    public static boolean bruteforce(String[] input) {
        for (int i = 0; i < input.length; i++) {
            for (int j = 0; j < input.length; j++) {
                if (input[i].equals(input[j]) && i != j) {
                    return true;
                }
            }
        }
        return false;
    }
    /*
     * detect duplicate in array by comparing size of List and Set
     * since Set doesn't contain duplicate, size must be less for an array which contains duplicates
     */
    public static boolean checkDuplicateUsingSet(String[] input){
        List inputList = Arrays.asList(input);
        Set inputSet = new HashSet(inputList);
        if(inputSet.size()< inputList.size()) {
            return true;
        }
        return false;
    }
  
    /*
     * Since Set doesn't allow duplicates add() return false
     * if we try to add duplicates into Set and this property
     * can be used to check if array contains duplicates in Java
     */
    public static boolean checkDuplicateUsingAdd(String[] input) {
        Set tempSet = new HashSet();
        for (String str : input) {
            if (!tempSet.add(str)) {
                return true;
            }
        }
        return false;
    }
}