Converting Octal to Decimal and then Decimal to Octal

ZackCampbell5 · #1 27-Oct-2009, 07:41

I am a beginner in computer programing using java. I was given a project in my college level class to create a program to convert Octal numbers to decimal numbers and decimal numbers to octal numbers. I have specific guidelines that i have to follow but the only thing that i can not figure out is the coding for converting the numbers. If i could get information on how to do this conversion using Strings and StdIn and not using reader buffers, that would be a great help.

this is what i have so far:

JAVA Code:

public class Project2
{
  public static void main (String[] args)
  {
    int Option;
    String Octal;
    String Decimal;
    System.out.println ("1. Decimal to Octal");
    System.out.println ("2. Octal to Decimal");
    System.out.println ("3. Exit");
    System.out.println ("Enter Your Menu Seclection (1,2,3): ");
    Option = StdIn.readInt ();
    while (Option != 3)
    {
      if (Option == 1)
      {
        System.out.println ("Please enter your Decimal: ");
        Decimal = StdIn.readString ();     
      }
      else if (Option == 2)
      {
        System.out.println ("Please enter your Octal: ");
        Octal = StdIn.readString ();


      }
      else 
      {
        System.out.println ("-----Option " + Option + " does not exist. Please select option 1,2, or 3.-----");
        System.out.println ("1. Decimal to Octal");
        System.out.println ("2. Octal to Decimal");
        System.out.println ("3. Exit");
        System.out.println ("Enter Your Menu Seclection (1,2,3): ");
        Option = StdIn.readInt ();
      }
    }
    if (Option == 3)
    {
      System.out.println ("Thank You. Good bye.");
    }    
  }
}

TurboPT · #2 27-Oct-2009, 20:46

Quote:

Originally Posted by ZackCampbell5

...If i could get information on how to do this conversion using Strings...

See the Java's String class API for various parse-ing methods.
...and also check the decode() function of the Integer class.

Quote:

Originally Posted by ZackCampbell5

... and not using reader buffers, that would be a great help.

How about the Scanner class? [requires Java 1.5 or higher] See this example.

ZackCampbell5 · #3 28-Oct-2009, 07:18

Well i was told that i have Java 1.6 but when i tried to run the program that you suggested (with the scanner import) i only got this message:

Code:

java.util.InputMismatchException
	at java.util.Scanner.throwFor(Unknown Source)
	at java.util.Scanner.next(Unknown Source)
	at java.util.Scanner.nextInt(Unknown Source)
	at java.util.Scanner.nextInt(Unknown Source)
	at ScannerTest.main(ScannerTest.java:30)

also i have done extensive research on the parse-ing method and do not understand how to code it.

is it possible to use some sort of array in the converting process?
>

TurboPT · #4 29-Oct-2009, 17:06

Huh?

The example runs fine for me:

Code:

C:\Documents and Settings\user\Desktop\OTH>"\Program Files\Java\jdk1.5.0_01\bin\javac.exe" ScannerTest.java

C:\Documents and Settings\user\Desktop\OTH>"\Program Files\Java\jdk1.5.0_01\bin\java.exe" ScannerTest
Enter int, double, word, line: 4 1.0 check this is only a test!
4:1.0:check: this is only a test!

...so I'm not sure what was done?

ZackCampbell5 · #5 30-Oct-2009, 07:27

Sorry i had several erros while trying to run the scanner. It works fine now thank you but how will i use the scanner to help me convert from octal to decimal? sorry like i said before i am a beginner

TurboPT · #6 30-Oct-2009, 08:37

Quote:

Originally Posted by ZackCampbell5

... but how will i use the scanner to help me convert from octal to decimal?

I don't know what your "specific guidelines" might be, but here is a small example with the Scanner in use:

JAVA Code:

import java.util.Scanner;  // for Scanner class

public class HexOctExample
{
    public static void main(String[] args) 
    {
        Scanner input = new Scanner(System.in);
        int aValue;

        System.out.print("Input a decimal number to convert: ");
        aValue = input.nextInt();

        System.out.println("The conversion:");
        System.out.println("...as HEX: " + Integer.toHexString(aValue)); 
        System.out.println("...as OCT: " + Integer.toOctalString(aValue)); 
    }
}

example interaction/output:

Code:

Input a decimal number to convert: 128

The conversion:
...as HEX: 80
...as OCT: 200

HTH.

EDIT:
Note that the example doesn't have exception [try/catch] handling around the input retrieval, but at this point, you probably have NOT covered exceptions yet, so I left that out.

ZackCampbell5 · #7 03-Nov-2009, 07:30

That Scanner import did work successfully for me but i do not think that i am allowed to use that. I think that i am supposed to go the long way around it by using this sort of method in my coding :
921/8 = 115, 921%8 = 1
115/8 = 14, 115%8 = 3
14/8 = 1, 14%8 = 6
1/8 = 0, 1%8 = 1
it may seem like a waste of time to do each of these individual steps but i think that this is what my instructor requires. if you could somehow show me how to code this to make it less of a pain to convert like this every time. Thank you.

TurboPT · #8 03-Nov-2009, 12:58

Quote:

Originally Posted by ZackCampbell5

it may seem like a waste of time to do each of these individual steps but i think that this is what my instructor requires.

NOT a waste of time. This is fundamental knowledge as to converting to other base values using basic operators from the language. I recall those days too, although it seems to be a "waste of time" now, it's all part of the learning, and is needed when one ever encounters a situation where (based on the limits of the targeted programming environment) a library cannot be used and you have to write a small routines yourself to do what you need. Also, as a professor once told us, "It is learning the hard way that makes you appreciate the use of libraries."

Quote:

Originally Posted by ZackCampbell5

if you could somehow show me how to code this to make it less of a pain to convert like this every time. Thank you.

Hint: Looking at the example data you gave, it nearly cries for loop handling. Setting up a loop can "ease the pain" of individual steps!

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Converting Octal to Decimal and then Decimal to Octal

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