Related Tags

java
permutation
factorial
communitycreator

# How to get the permutation of a number in Java

okwudili onyejiaku

### Overview

A permutation is the number of ways by which we can arrange a set or an object in a definite order. The mathematical formula to calculate a permutation is given below:

The formula for permutation in Java

### Parameters

• P: This is the number of permutations.
• n: This is the number of objects.
• r: This is the number of objects selected.

We must use the above formula to get the permutation for multiple objects. We obtain the permutation by defining the factorial for n and n-r.

Here is the syntax to get the factorial using a for loop.

### Syntax

for(counter; counter <= number; counter++)
{
result = result * counter;
}
Syntax for finding the factorial of a number

### Parameters

counter: This represents a counter. The function will use it for looping.

number: This is the input number for which we're trying to find the factorial.

### Code

class HelloWorld {
// create the factorial function
public static int factorial(int num){
int result = 1, counter;
// create for loop
for(counter=1; counter<=num; counter++){
result = result*counter;
}

return result;
}

public static void main( String args[] ) {
// create some numbers of objects we want to get the combination
int n1 = 7;
int n2 = 4;

// create number of the objects are taken at a time
int r1 = 3;
int r2 = 2;

// get the permutation based on the mathematical formula
System.out.println(factorial(n1)/(factorial(r1)*factorial(n1-r1)));
System.out.println(factorial(n2)/(factorial(n2-r2)));
}
}
Code to get the permutation of a number in Java

### Explanation

• Line 3: We create a factorial() function that takes an integer number and returns its factorial.
• Lines 15 and 16: We create and initialize variables for the number of objects we want to get combinations of.
• Lines 19 and 20: We create and initialize the number of objects taken at a particular time for every selection.
• Lines 23 and 24: We use the mathematical formula for combinations to obtain the permutations and print the values to the console.

RELATED TAGS

java
permutation
factorial
communitycreator

CONTRIBUTOR

okwudili onyejiaku
RELATED COURSES

View all Courses

Keep Exploring

Learn in-demand tech skills in half the time 