# 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)
{
}
}

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 🙂