A little lost with for loops and making a design

[LinxuS]

Ask the user to enter a number between 4 and 20. If the user enters a number outside that range ask them for the number again. Based on the number the user enters, print a triangle of stars as in the following example:
If the user enters 5, your program would print the following:

Quote:

*
**
***
****
*****

(except the alignment is to the right)
so basically..
____*
___**
__***
_****
*****
without the _

So far, I've got the error checking alright, but I don't really know where to start with for the stars.

Quote:

public static void main(String [] args)
{
Scanner k = new Scanner(System.in);
System.out.println("Please enter a number between 4 and 20");
int num = k.nextInt();

while(num < 4 || num > 20)
{
System.out.println("Oops! Your number is not between 4 and 20, enter another one");
num = k.nextInt();
}
}

I'm assuming it involves a for loop, with a System.out.print(" "); System.out.print("*"); and a System.out.println("");

but any more than that I'm not sure..

[hardwired]

Code:

        int n = 5;
        for(int j = 0; j < n; j++)
            System.out.print("*");
        System.out.println();

You just have to play around with print statements and loops. Imagination and play are the keys to this kind of discovery/exploration.

[dejavujr]

int n = 5;
for(int j = 0; j < n; j++)
{
for (int x = 0; x<=j ; x++) {
System.out.print("*");}

System.out.println();}

will dispaly
*
**
***
****
*****

[LinxuS]

well I got this so far..:

for(int l = 0; l < num; l++)
{
for (int a = 0; a <= l; a++)
System.out.print(" ");

for (int x = 0; x<=l ; x++)
{
System.out.print("*");
}
System.out.println();

}

but the spaces are in reverse order that they need to be..

[CaptainMorgan]

Welcome to the Java Forums. I appreciate you making a valid attempt at your work.

When working out code like this, there is no better way to get this structure into your head(when you are first starting out), than to get a pencil and a piece of paper and draw out what exactly is going on. Also, choose your variable names wisely.. I changed it to lowercase i because I couldn't figure out if you were using uppercase I, lowercase L or a number one. Cheers.

Please use code tags.

Code:

    int num = 5; 
    int spaces = 5;
    for(int i = 0; i < num; i++) {
      for (int a = spaces - 1; a > 0; a--)
        System.out.print(" ");

      for (int x = 0; x <= i; x++) {
        System.out.print("*");
      }
      System.out.println();
      spaces--;
    }

See you around!

[tim]

To use code tags you:
You select your code, and click the hash (#) icon when in advanced mode.