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Posted on 2003-11-19
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Last Modified: 2010-03-31
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
0
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Question by:dirtydinny
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9 Comments
 
LVL 35

Accepted Solution

by:
TimYates earned 50 total points
ID: 9779140
something like:

-----------

import java.text.* ;

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

    DecimalFormat df = new DecimalFormat( "0.##########E00" ) ;
    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
      String sAnswer = df.format( answer ) ;
      while( sAnswer.length() < 15 )
        sAnswer = " " + sAnswer ;
      System.out.println( n + "\t" + sAnswer ) ; //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
0
 
LVL 35

Expert Comment

by:TimYates
ID: 9779260
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
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9779600
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
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LVL 35

Expert Comment

by:TimYates
ID: 9779644
you and your BigIntegers ;-)
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9779948
Yes, maybe i should create a subclass called 'BigPal' - i'm surprised it isn't final
0
 
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Expert Comment

by:TimYates
ID: 9780028
Ooooh...me too >_<
0
 
LVL 92

Expert Comment

by:objects
ID: 9782141
long answer = 0;
for (byte n=1; n<64 && (answer=(long) Math.pow(2, n))<10000000000L; n++)
{
0
 
LVL 92

Expert Comment

by:objects
ID: 9782226
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.
0
 
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Expert Comment

by:objects
ID: 9782450
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);
}
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