A lil help!

MidnightQueen

I'm just kinda stuck at the mo. I know this will come up in the exam tomorrow but i cant remember how to do it.

Write a program to Print out the following using Loops in Java. I know its a for loop. Heres the pattern.

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

Heres the code i already have written:

public class Stars
{
public static void main(String args[])
{
int i, j;
for(i=0; i<10; i++)
{
for(j=0; j<10; j++)
{
System.out.print("*");
}

System.out.println();
}
}
}

but it keeps printing out like this:

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

MrPinK

You want to inner loop to print i + 1 stars on each line basically

Chad ghostal

Havent tried it, but it looks like j should be incremented in the outer 'i' loop and not in its own loop..if you get me..

Trojan

It sure does. Think about why it's printing 10 on the 1st line.

You want to print 1 on the 1st, 2 on the 2nd, 3 on the 3rd, right? What variables do you need to use while printing?

btw if you use [ code ] tags around segments it'll show properly.

--

Aside: If anyone gives a straight solution on this thread without helping the (OP) student learn something their prize is a ban from Programming

MrPinK

Trojan wrote:

Aside: If anyone gives a straight solution on this thread without helping the (OP) student learn something their prize is a ban from Programming

I'd usual agree with the "teach a man to fish..." arguement, but it looks like (s)he is doing some last minute exam cramming. Have a heart

Trojan

Bah, should have some clue. It's simple logic, though for a 1st year with summer exam tomorrow it might be tough.

I retract the prize as offered.

Chad ghostal

meh... if ..kittykat still needs it...
which is unlikely..

(only took me 3 goes )

public class Stars {

  public static void main(String args[])
  {
  int i, j;
  for(i=0; i<10; i++)
  {

  for(j=0; j<i+1;j++ )
  {
  System.out.print("*");
  }

  System.out.println();
  }
  }
}

tempest

Trojan wrote:

Bah, should have some clue. It's simple logic, though for a 1st year with summer exam tomorrow it might be tough.

I retract the prize as offered.

I think you were right regardless of cramming.

The exam could well consist of a question based on the thought processes used in the first, (although experience implies otherwise).

For example, somebody here writes the code and then the exam says that the output should be:

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

If the answer is given then the OP will not have gained the necessary approach to solve this themselves.

tbph, and IMHO, the most information that should be given is to comment each line of code.

public class Stars
{
  public static void main(String args[])
  {
    int i, j; // Counter for the inner and outer loops.. maybe these can be named better? line, starCounter

    // For each line that I have to print stars on
    for(i=0; i<10; i++)
    {
      // For 10 stars? 
      for(j=0; j<10; j++)
      {
        // Print a single star
        System.out.print("*");
      }

      // Move to the next line
      System.out.println();
    }
  }
}

MidnightQueen

Chad ghostal wrote:

for(j=0; j<i+1;j++ )

Thanks for solving the problem. I knew i was missing something. Thanks for that! It should come up in the exam i hope.

Trojan

KittyKat wrote:

Thanks for solving the problem. I knew i was missing something. Thanks for that! It should come up in the exam i hope.

I'm not convinced this was a worthwhile exercise...

BizzyC

If you do it this way, it'll work in both directions.

  int x= 1; //set to 10 if you need to print reverse pyramid 
 for(int i =0; i<10; i++)
 {
   for(int a=0;a<x;a++)
   {
      System.out.print("*");
   }
   System.out.println("");
   x++; // set to x-- if pyramid is in reverse order.
 }

Should print
*
**
***
****
*****
******
*******
********
*********
**********

change x values as stated and it should give the reverse.

MidnightQueen

Sorry to say it didnt come up in the exam. Pitty cos i was hoping it would come up. Nested Loops came up instead. Thanks for all the help! If theyre was still rep going around i would still give some to all.

BizzyC

Is a for loop inside another loop not a nested loop???

MidnightQueen

Ok ya you're rite.* For loops did come up, but i was hoping that they would have the Question to "print a Triangle using loops" would come up and it didnt.







*smartass!

BizzyC

Was I being a smartass!?!:p

MidnightQueen

U are now!*






*Goes to fetch the whip.










Nah i'm only messing! Thanks for trying to help out.

BizzyC

Hope you passed.
Good luck.

rsynnott

KittyKat wrote:

I'm just kinda stuck at the mo. I know this will come up in the exam tomorrow but i cant remember how to do it.

Ah, I wish my exams were going to be like that...

zap

if you were doing the exam i did, it was very easy and a q like that did come up except it was numbers instead of stars.

MidnightQueen

BizzyC wrote:

Hope you passed.
Good luck.

Thanks!

zap wrote:

if you were doing the exam i did, it was very easy and a q like that did come up except it was numbers instead of stars.

Ya i hate the ones with numbers.

uber

For what it's worth, here's the one loop version.
Can it be done any shorter? (style notwithstanding)

public class Stars
{

    public static void main(String[] args)
    {
        //the accumulator
        String ssOutput = new String();
        // the character for the pattern
        String ssCHAR_TO_OUTPUT = new String("*");
        // the count of lines
        int iNumLines = 10;
        //loop around
        for ( int i = 0 ; i < iNumLines; i++)
        {
            //add the character to the accumulator
            ssOutput += ssCHAR_TO_OUTPUT;
            //print out the accumulator with the newline
            System.out.println(ssOutput);
        }
    }
}

bonkey

uber wrote:

Can it be done any shorter?

Don't think so, but you could probably improve performance by generating it entirely in memory (line-feeds included) and writing once.

Or, you could do it all ultra-dirty stylee, which is effectively still just your code.

 public static void main(String[] args)
	{
		for ( String ssOutput= new String() ; ssOutput.Length < 10 ; system.out.println(ssOutput+="*") );
	}

Thats just nasty though

Hobbes

uber wrote:

For what it's worth, here's the one loop version.
Can it be done any shorter? (style notwithstanding)

You should be using StringBuffer.

ressem

Now you've gone and done it,

I might as well be the first to suggest
"*\n**\n***\n****\n...


For short,
How about set ssCHAR_TO_OUTPUT to "**********"
and use a substring in the loop

System.out.println(ssCHAR_TO_OUTPUT.substring(i))

No superflous manual new, or string/stringbuffer argument.
Get promoted before you have to maintain it tho.

GreeBo

ressem wrote:

No .....string/stringbuffer argument.

substring will create a new String object each time....

rsynnott

Where on earth did you dig this up from?

GreeBo

sometimes being right is more important than being timely...

rsynnott

GreeBo wrote:

sometimes being right is more important than being timely...

Is it relevant, though? He didn't say it didn't create an object.

Hobbes

rsynnott wrote:

Is it relevant, though? He didn't say it didn't create an object.

Hes right. Every time you make a reference to create/update a string it always creates a new object which is wasteful. StringBuffer doesn't.

Of course both will work though and for such a tiny program its no big deal but you might as well learn correctly from the start.

I like the "*\n**\n***\n..." approach though.

rsynnott

Hobbes wrote:

Hes right. Every time you make a reference to create/update a string it always creates a new object which is wasteful. StringBuffer doesn't.

Of course both will work though and for such a tiny program its no big deal but you might as well learn correctly from the start.

I like the "*\n**\n***\n..." approach though.

He's right, all right, at least theoretically. I believe, though, that at least Sun's compiler has optimised inappropriate use of String to StringBuffer for some time now.

GreeBo

rsynnott wrote:

I believe, though, that at least Sun's compiler has optimised inappropriate use of String to StringBuffer for some time now.

Is it smart enough to catch looped substring calls?
If it is thats impressive.