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 functionpublic static int factorial(int num){int result = 1, counter;// create for loopfor(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 combinationint n1 = 7;int n2 = 4;// create number of the objects are taken at a timeint r1 = 3;int r2 = 2;// get the permutation based on the mathematical formulaSystem.out.println(factorial(n1)/(factorial(r1)*factorial(n1-r1)));System.out.println(factorial(n2)/(factorial(n2-r2)));}}

- 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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