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Need Help (again)- GETTER METHOD: Need to identify all integers divisible by the Prime, removed from one list and added to another list.   ADVISE on where to begin....

Posted on 2007-11-25
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Last Modified: 2010-04-21
Hi again, to those who helped me earlier.  

I have a getter method began, but I'm not sure how to go about the code.  Honestly, I'm so new to Java... I'm not very familiar with getter methods as well as incorporating the usage of modulus operators... %  

Please help......  at least where to begin...

   public static void getComposites(ListInterface<Integer> candidates, ListInterface<Integer> composites, Integer prime)
          {
            //if prime is divisible by candidates    
               //candidates.remove
            // and add to composites list....
           
       }  

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Question by:ahowe01
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LVL 92

Expert Comment

by:objects
Comment Utility
try something like:

for (int i=candidates.getLength()-1; i>=0; i--)
{
   Integer value = candidates.getEntry(i);
   if (prime.intValue() % value.intValue()==0)
   {
        // prime divisible by value
        candidates.remove(i);
        composites.add(value);
   }
}
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Author Comment

by:ahowe01
Comment Utility
What would cause my program to not be able to identify the get method when I call it?

       //  Displays Composites List
       compositesList.getComposites();
       System.out.println("Composites List:   ");
       System.out.println(compositesList);

then the error says;  cannot find symbol method getComposites()

Maybe I should have started the call first..... instead of attempting to finish the getter method? ?  
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LVL 92

Accepted Solution

by:
objects earned 500 total points
Comment Utility
>        compositesList.getComposites();

u need to pass the listed arguments

       compositesList.getComposites(candidates, composites, prime);
0
 

Author Comment

by:ahowe01
Comment Utility
see I new there was something simple....  

but why does it say:  cannot find symbol variable candidates
                                   cannot find symbol variable composites
                                   cannot find symbol variable prime
 
do I need to declare them, even though the getter method declares them as an integer?
0
 
LVL 92

Expert Comment

by:objects
Comment Utility
use the name of whatever variables you are using for the 2 lists, and the prime number
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Author Comment

by:ahowe01
Comment Utility
???   Hi again... Will you look at the remaining of my code and give more guidance, please.    I'm reading up now on getter and setter method.     I'm working on this program in baby steps, piece by piece.  

thank you.  
import java.io.*;

import java.util.*;
 
 

public class Primes {
 

    public static void main( String args[] )   

     {

        int max; 

 

        	       

        System.out.println( "Please enter the maximum value to test for primality" );

        max = getInt("   It should be an integer value greater than or equal to 2.");

        

       // Creates Prime List 	

       ListInterface primeList = new AList();

      

       //  Creates Composites List

       ListInterface compositesList = new AList();      

 

       // Creates Candidate List 

        ListInterface candidateList = new AList();

        

        

        candidateList.add(2);

        candidateList.add(3);

        candidateList.add(4);

        candidateList.add(5);

        candidateList.add(6);

        candidateList.add(7);

        candidateList.add(11);

        candidateList.add(13);

        candidateList.add(17);            	

         

    //  System.out.print(max);    

   for (int position = candidateList.getLength(); position>=0; position--)

   {

        Integer index = (Integer)candidateList.getEntry(position);

        if (index > max)

      {

       candidateList.remove(position);

      }

      else

      {

      	break;

      }

   }

     

       System.out.println("   ");      

       System.out.println(candidateList);                        

                                                             

       //Remove first Prime number from candidateList   

       Object o = candidateList.remove(1);

       if (o != null) {

       	primeList.add(o);

       }
 

        // Displays New Candidate List

       System.out.println("   ");  

       System.out.println("New Candidate List: ");

       System.out.println(candidateList);

    

       //  Displays Prime List

       System.out.println("   "); 

       System.out.println("Prime List:");	

       System.out.println(primeList); 

       	

       //  Displays Composites List

       compositesList.getComposites(candidate, composites, prime);

       System.out.println("Composites List: ");

       System.out.println(compositesList);	 

     }   		   

    

    /**

     * getComposites - remove the composite values from possibles list and

     * put them in the composites list

     *

     * @param  possibles   a list of integers holding the possible values

     * @param  composites   a list of integers holding the composite values

     * @param  prime   an Integer that is prime

     */

    

   public static void getComposites(ListInterface<Integer> candidates, ListInterface<Integer> composites, Integer prime) 

    	{

            //if prime is divisible by candidates     

         	//candidates.remove

            // and add to composites list....
 

            	for (int i=candidates.getLength()-1; i>=0; i--)

                {

                Integer value = candidates.getEntry(i);

                if (prime.intValue() % value.intValue()==0)

                   {

                 // prime divisible by value

                 candidates.remove(i);

                 composites.add(value);

                   }

                }

       }   	       

   

   	

    /**

     * Get an integer value

     *

     * @return     an integer 

     */

     

    private static int getInt(String rangePrompt)

    {

        Scanner input;

        int result = 10;        //default value is 10

                

        try

        

        {

            input = new Scanner(System.in);

            System.out.println(rangePrompt);

            result = input.nextInt();

            

        }

        

        catch(NumberFormatException e)        

        {

            System.out.println("Could not convert input to an integer");

            System.out.println(e.getMessage());

            System.out.println("Will use 10 as the default value");

        }        

        

        catch(Exception e)

        

        {

            System.out.println("There was an error with System.in");

            System.out.println(e.getMessage());

            System.out.println("Will use 10 as the default value");

        }

        

        return result;

                                 

    }    

    

}

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Author Comment

by:ahowe01
Comment Utility
Do I need to set up a set method... is that something that should always be with a get method?  
0
 
LVL 92

Expert Comment

by:objects
Comment Utility
not necessarily.
and your get methods are not really getters, typically a getter method simply returns the value of a property of an object.
0
 

Author Comment

by:ahowe01
Comment Utility
ok, so I'm still stuck...  (And having nightmares... I wish I could learn java like you experts....)

You say I need to pass the arguments listed with the name of my viarables....

I have initialized in my main-

 int prime;
ListInterface compositesList = new AList();  
 ListInterface candidateList = new AList();

so in the main to call my getcomposite i've tried to called them as;

compositesList.getComposites(candidateList, compositesList, prime);

But I still error out....

other advise.... or website that is a good tool to understanding better.  I have the deitel book so that's helping a little bit.

0
 

Author Comment

by:ahowe01
Comment Utility
nevermind... I see what I was doing wrong....  

thanks... until next time. :)
0
 

Author Closing Comment

by:ahowe01
Comment Utility
Thanks....
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