Find Number of Combinations in Java

Finding no. of Combinations in Java
This lets you find no. of combinations in java using the standard nCr forumla. This is a simple logic.

The formula of nCr is n!/(n-r)!r!

import java.util.*;
class FindCombination
    public static void main(String args[])
    Scanner s=new Scanner(;

    System.out.println("Enter the value of n");
    int n=s.nextInt();
    System.out.println("Enter the combination suffix (r)");
    int r=s.nextInt();

    long res=1;

            System.out.println("The result is "+res);
        else System.out.println("r cannot be greater than n");

    public static long getFact(int n)
        long f=1;

        for(int i=n;i>=1;i--)

    return f;

Sample Output

Enter the value of n
Enter the combination suffix (r)
The result is 21


n>=r: n cannot be greater than the suffix r in a combination.
getFact(n)/(getFact(n-r)*getFact(r)): This is the formula n!/((n-r)!.r!).
getFact() method has been explained in finding the factorial of a number in Java post.

Also see Permuting a number in Java using formula
This is the way in which we can calculate the number of combinations nCr is calculated provided the value of n and r.

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Tags: Playing with Numbers,