Thread: Factorial of a Number (program completed but doubt in that)

Friends please help me out to solve this problem .....
1 import java.io.*;
2 class Factorial
3 {
4 public static void main(String args[]) throws IOException
5 {
6 System.out.println("Enter a value=");
7 DataInputStream a =new DataInputStream(System.in);
8 int b=Integer.parseInt(a.readLine());
9 int result=frac(b);
10 System.out.println("The factorial of "+b+" is " +result);
11 }
12 public static int frac(int a)
13 {
14 int j=a;
15 for(int i=1;i<j;i++)
16 {
17 a=a*(j-i);
18 }
19 return a;
20 }
21 }
Actually the program is perfectly running but ..
Problem is that [B]In LIne no.-15 if i replace j by a , like for(int i=1;i<a;i++) the result was totally different (was showing output as 0) ....
my objective is :- why it has different output thow j and a have same value .... [/B]

Please post your code in code tags.

I don't understand why you're asking, "If I change my code, why does the output change?" Isn't that expected, even obvious? Can you state your question more clearly?

Frankly, 'j' is completely unnecessary, at least the way you're using it.

I recommend you use a Scanner object vice a DataInputStream.

my doubt even "a" and "j" in the block have same value but while replace "j" by "a" why the output gets changed ....

--- Update ---

my doubt is even "a" and "j" in the block have same value but while replace "j" by "a" why the output gets changed ....

Originally Posted by GregBrannon

Please post your code in code tags.

I don't understand why you're asking, "If I change my code, why does the output change?" Isn't that expected, even obvious? Can you state your question more clearly?

Frankly, 'j' is completely unnecessary, at least the way you're using it.

I recommend you use a Scanner object vice a DataInputStream.

Trace your code. Pick a small value of 'a', like 4 or 5, and construct a table that contains the value of each variable, i, j, and a after each for loop completes for both cases. You will see that even though j and a may start off with the same value, values change as the for loop executes, causing the results to vary.

Exploring results you're uncertain about in this way is how you learn and understand what happens rather than have someone explain it to you in a way you may not understand, is just plain wrong, or you'll forget tomorrow because you didn't figure it out yourself.

Good luck, keep coding, and keep being curious - but answer most of your questions yourself.

1 import java.io.*;
2 class Factorial
3 {
static int b;
4 public static void main(String args[]) throws IOException
5 {
6 System.out.println("Enter a value=");
7 DataInputStream a =new DataInputStream(System.in);
8 b=Integer.parseInt(a.readLine());
9 int result=frac(b);
10 System.out.println("The factorial of "+b+" is " +result);
11 }
12 public static int frac(int a)
13 {
14
15 for(int i=1;i<a;i++)
16 {
17 a=a*(b-i);
18 }
19 return a;
20 }
21 }


now the output is zero why soo please tell me @Gregbranon

--- Update ---

1 import java.io.*;
2 class Factorial
3 {
static int b;
4 public static void main(String args[]) throws IOException
5 {
6 System.out.println("Enter a value=");
7 DataInputStream a =new DataInputStream(System.in);
8 b=Integer.parseInt(a.readLine());
9 int result=frac(b);
10 System.out.println("The factorial of "+b+" is " +result);
11 }
12 public static int frac(int a)
13 {
14
15 for(int i=1;i<a;i++)
16 {
17 a=a*(b-i);
18 }
19 return a;
20 }
21 }


now the output is why soo please tell me

Originally Posted by GregBrannon

Trace your code. Pick a small value of 'a', like 4 or 5, and construct a table that contains the value of each variable, i, j, and a after each for loop completes for both cases. You will see that even though j and a may start off with the same value, values change as the for loop executes, causing the results to vary.

Exploring results you're uncertain about in this way is how you learn and understand what happens rather than have someone explain it to you in a way you may not understand, is just plain wrong, or you'll forget tomorrow because you didn't figure it out yourself.

Good luck, keep coding, and keep being curious - but answer most of your questions yourself.

Thank your GregBrannon, thanks for your helpful advice, i shall take care of it... By the way problem is solved, there was a silly mistake ....

I'm glad you figured it out. We often learn more by finding and correcting our own "silly" mistakes than we do by being perfect every time.