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okwudili onyejiaku

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:

**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.

for(counter; counter <= number; counter++) { result = result * counter; }

Syntax for finding the factorial of a number

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

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

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

- 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.

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java

permutation

factorial

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