print n numbers

[Jack Bolton]

Hi,
I am working in this program that is suppoused to print the firsts numbers from a series of numbers:
1,5,9,13,17...etc..
So, the numbers are jumping from 4 to 4.
for example:
if the user enters "1",the program prints 1.
if the user enters "2", the program prints 1 and 5.
and so on.

how can i program this?

thanks for any response...

[Jeanne Boyarsky]

Jack,
What do you have so far? A good approach to starting is to try solving a similar, but simpler problem. For example, can you have the user enter a number and print it out? Can you print out the numbers from 1 to "n" without skipping?

[marc weber]

It often helps to describe the process in English before trying to code in Java. For example, you might say something like...

Output a number.

Check to see if you're done (if you've output n numbers).

If you're done, then stop.

If you're not done, then add 4 (or whatever interval you're using) to the previous output.

Repeat.

Once you have the process (algorithm) described, then you can start writing code to match the steps.

Give this a try, and let us know what you come up with.

[colin shuker]

There are several ways to solve this, and I won't tell you because it is forbidden in java ranch.

But heres some tips
You will need a way to enter how many numbers you want.
JOptionPane is probably best, but you could just do:
int num=2;
just for testing.

Then you are going to need a loop.
You could use while loop or for loop, I recommend for loop here.

Next, I guess you need a formula, well the n'th term will be 4n-3 if n is starting at 1, but you might prefer to start at 0 which is the traditional way to start a for loop.

[Stan James]

The hint for the "for loop" is probably just what the original poster needed. I did a quick Google for "java for loop" and hit THIS SITE. Try the example on this page and make sure you know how it works. Follow the "next" link to the "while loop" tip.

[Jack Bolton]

This is what I've done so far, but,
something is missing: this program is suppoused to print the firsts numbers from a series of numbers:
1,5,9,13,17...etc..(as I said before),
so, if the user enters, for example: "3", the program should print the first "3" numbers that are: 1,5,9.
but,
Right now, if the user enters "3", the program only prints: "1".
what can i do to solve this?
thanks for any response...
the code:

import java.io.*;
 
public class Tor{

public static void main(String[]args) throws IOException{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

int inp;
System.out.println("Enter the number:");
inp=Integer.parseInt(br.readLine());
int i;
for ( i=1; i<=inp; i+=4 ) {
     System.out.println(i);
}
}
}

[ May 15, 2007: Message edited by: Jack Bolton ]

[Campbell Ritchie]

Whoever said the problem is in the "for" loop was correct. Go through your "for" loop with a debugger, or use a pencil and say, "When I start the number i is 1, then i becomes . . . " until you work out exactly what is happening in the "for" loop.

[colin shuker]

Thats right, take a look at your for loop.
There are many ways to solve this, seems you are not going with the formula approach I mentioned a few posts ago, but with a continual incrementing approach.
But if you use an incrementing approach, then you don't want to be incrementing the loop variable, but you will need some other variable, perhaps initialized to 1 to start with, then you can increment by 4 each time you go through the loop.

Your code seems a little ironic, in that you are using complicated things like BufferedReader, and InputStreamReader, and that you don't quite grasp how to solve this loop, or perhaps thats just how you were told to grab data.

Good luck with it anyway.

[Jenn Person]

Originally posted by Jack Bolton:

for ( i=1; i<=inp; i+=4 ) {
     System.out.println(i);
}
}

Check your for loop. Trace through each loop, paying careful attention to the value of your i variable as you go along, and take a look at your loop condition as well. You'll see why it only prints once when you enter 3.