# Co-Primes in Java

In this tutorial, we will learn to distinguish co-primes from non-co-primes and implement it in Java.

So what exactly are Co-Primes?

## Co-Primes

When two numbers have no common factor except “1” then such a pair of numbers are called as Co-primes.

Hence in simple words, if the **HCF** of the two numbers is **1**, then they are called as Co-primes.

Co-primes are also called as **Relatively Prime** or **Mutually Prime**.

**Note**: These two numbers may or may not be prime

### Explanation of Co-Primes or not with example

#### Example 1:

Let number1: 5

Let number2: 50

Factors of number1 are: 1, 5

Factors of number2 are: 1, 2, 5, 10, 25, 50

HCF is 5

Hence they are *Not Co-Primes*.

#### Example 2:

Let number1: 14

Let number2: 15

Factors of number1 are: 1, 2, 7, 14

Factors of number2 are: 1, 3, 5, 15

HCF is 1

Hence they are *Co-Primes*.

## Code for Finding Co-Primes or not in Java

import java.util.*; class coprimes { public static void main(String[]args) { Scanner scan = new Scanner(System.in); System.out.print("Enter number 1: "); int num1 = scan.nextInt(); ArrayList<Integer> arr1 = new ArrayList<Integer>(); System.out.print("Enter number 2: "); int num2 = scan.nextInt(); ArrayList<Integer> arr2 = new ArrayList<Integer>(); for(int i = 0, j = 2; i < num1 ; i++, j++) { if(num1 % j == 0) // for finding factors { arr1.add(j); //storing the factors in a list } } for(int i = 0, j = 2; i < num2; i++, j++) { if(num2 % j == 0) { arr2.add(j); } } if(num2 > num1) { arr2.retainAll(arr1); //retains all the common elements in both the lists in arr2 boolean isEqual = arr1.equals(arr2); if(isEqual) { System.out.println("Not Co-Primes"); } else { System.out.println("Co-Primes"); } } else { arr1.retainAll(arr2); //retains all the common elements in both the lists in arr1 boolean isEqual = arr1.equals(arr2); if(isEqual) { System.out.println("Not Co-Primes"); } else { System.out.println("Co-Primes"); } } } }

#### Output:

Enter number 1: 2 Enter number 2: 3 Co-Primes

Hope you’ve understood the code ðŸ™‚

Any questions feel free to drop in your comments

You can also check other posts:

## Leave a Reply