Find factorial using java program.

            let us find the factorial of the number using java program. For that, we should learn what is factorial of a number and what is the logic we should put in the program.

Content.

1. What is factorial of a number?
2. Logic for the program.
3. Program.
4. Explanation of program.
5. Output
6. Task.

What is factorial of a number?

            Let us have a number n, the product of all the positive numbers until the number is known as factorial of the number.

    formula:

                n!=n*(n-1)*(n-2)*......*1.

    example:

                5! = 5*(5-1)*(5-2)*(5-3)*(5-4).   

                5! = 5*4*3*2*1.                         (remember until one)

                5!=120.

Logic for the program.

There are 3 points to make the program work

• First, assign a value for n.
• Second, subtracted until we have 1.
• Third, multiply the subtracted number.

Program to find the factorial.

    class fact 

    {

       public static void main( String args[])

         {

            int i,n,f=1;

            n=Integer.parseInt(args[0]);

            for(i=1;i<=n;i++)

               {

                  f=f*i;

               }

             System.out.println("fact=" +f);

         }

    }

Explanation of the program.

• We have given the class name has fact.
• public static void main(String arg[]) refers to add a method to the program.
• int i,n,f is declaring the variable and f is initialize with a number 1.(read further to know why?) n is the we give. i is used in formula.
• n=Integer.parseInt(args[0]) is used to convert array of numbers to primitive integer.
• Now, we have to give condition which satisfies all the 3 point above int the logic for the program.
• I choose, for loop to satisfy the condition.
• f*i is the formula.
• System.out.println is used to display the given in output screen(make sure S in System is capital)

know more about for loop here.

Point to be noted:

        It is a command line program, that is we will choose the number for which we wanted to find factorial at run time of the program.

example: java fact 3

Output:

        compile :  javac fact.java

        run         :  java fact 5

                        fact= 120

known how to execute java program here.

Task to complete:

        Try the above program, and find the factorial for other number. note integer is limited memory location.