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hey,

i'ver develop a programme using a while and for loop to diplay in a table the results of 2^n where 1<=n<64.

However i don't know how to modify the loop to limit the resuts to 10 digits. Also i wish to right align the numbers displayed in the n column.

If anyone knows how to do this, please let me know. If ye want to jazz up the presentation too fire away! thanks!

Here is my code:

/*Computes 2^n where 1<=n<64 and displays in a table*/

class Numbers
{
      public static void main(String[] args)
      {
            byte n = 1;      //declare n, the power, as a byte. initialised at 1 and will not excced 64
            double answer;      //solution of 2^n

            System.out.println("n \t2^n"); //print header of table output

            while (n<64) //iterate loop while n is less than 64
            {
                  answer = Math.pow(2,n); // set answer to 2^n
                  System.out.println(n + "\t" + answer); //print answer
                  n++; //increment n by 1
            } // end of while loop


            /*for (n=1; n<64; n++)
            {
                  answer = Math.pow(2,n); // set answer to 2^n
                  System.out.println(n + "\t" + answer); //print answer
                  n=n++; //increment n by 1
            }//end of for loop*/


      }//end of main
}//end of class

Thanks as ever

Dinny

ASKER CERTIFIED SOLUTION

TimYates

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TimYates

Hope this is sort of what you wanted...

btw, the DecimalFormat bit limits it to 10 decimal places, and the while loop pads the strings out to a max of 15 chars :-)

Tim

CEHJ

You'll get better output with a BigInteger:

import java.text.* ;
import java.math.BigInteger;

class Numbers
{
      public static void main( String[] args )
      {
            BigInteger bi = new BigInteger("2");
            System.out.println( "n \t\t\t2^n" ) ; //print header of table output
            System.out.println("---------------------------");
            for(int i = 1;i < 64;i++) {
                  String current = bi.pow(i).toString();
                  while(current.length() < 19)
                        current = " " + current;
                  System.out.println(i + "\t" + current);

            }
      } //end of main
} //end of class

TimYates

you and your BigIntegers ;-)

CEHJ

Yes, maybe i should create a subclass called 'BigPal' - i'm surprised it isn't final

TimYates

Ooooh...me too >_<

Mick Barry

long answer = 0;
for (byte n=1; n<64 && (answer=(long) Math.pow(2, n))<10000000000L; n++)
{

Mick Barry

This'll right align your numbers:

StringBuffer out = new StringBuffer();
out.setLength(10 - s.length());
out.append(s);

I'd also suggest not using tabs to align your table and instead add the number of spaces you require.

Mick Barry

public static void main(String[] args)
{
long answer = 0;
for (byte n=1; n<64 && (answer=(long) Math.pow(2, n))<10000000000L; n++)
{
rightAlignValue(n, 2);
rightAlignValue(answer, 15);
System.out.println();
}
}

private static void rightAlignValue(long value, int len)
{
String s = Long.toString(value);
StringBuffer out = new StringBuffer();
out.setLength(len - s.length());
out.append(s);
System.out.print(out);
}