My program is not computing the right output, and I'm not sure why

Question

I've been staring at this program for hours, maybe a second perspective could help.

import java.util.Arrays;
import java.util.Random;

public class Examples

{
private int numbers[]; 
private String result;

     public Examples()
        {
     numbers = new int[10];
         Arrays.fill(numbers, 42);
        } 

        public Examples(int[] array)
        {
        numbers = Arrays.copyOf(array, array.length);
        }


 public void setNumbers (int numbers) 
    {                                           
    this.numbers = new int[numbers];
    }
 public int [] getNumbers()
 {                                      
    return numbers;
 }



public  String toString()
{
    String result = new String();
    int i;                                  
    for (i = 0; i < numbers.length; i++)
        result = numbers + "\t";
        return result;
}

I'm supposed to create a class that stores integer and then prints out a certain output depending on what static void main method I am provided with. The one I am currently on is,

{
   public static void main( String [] args )
   {
      int i;
      FunkyNumbers funNumbers, moreFun;

      System.out.println("FunkyClientA:");
      System.out.println("Test default constructor and toString method");
      System.out.println();

      funNumbers = new FunkyNumbers();
      System.out.println("toString result from funNumbers:");
      System.out.println( funNumbers.toString() );
      System.out.println();

      moreFun = new FunkyNumbers();
      System.out.println("toString result from moreFun:");
      System.out.println( moreFun.toString() );

   } // end of method main

} //

The result is supposed to be Test default constructor and toString method

toString result from funNumbers: 42 42 42 42 42 42 42 42 42 42

toString result from moreFun: 42 42 42 42 42 42 42 42 42 42

however I get, Test default constructor and toString method

toString result from funNumbers: [I@6e1408

toString result from moreFun: [I@e53108

Where happens in your FunkyNumbers constructor? That is the one that is being called... — Joel, Nov 07 '12 at 21:38
We can help you, after you show us your code of the `FunkyNumbers` class... — jlordo, Nov 07 '12 at 21:49

Yogendra Singh · Answer 1 · 2012-11-07T21:50:40.160

Issue: You are always assigning a new value to result and not appending.

Better to use StringBuilder as :

    StringBuilder result = new StringBuilder();
    for (int i = 0; i < numbers.length; i++)
        result.append(numbers + "\t");
    return result.toString();

If don't want to use StringBuilder then

    String result = new String();
    for (int i = 0; i < numbers.length; i++)
        result = result + numbers + "\t";//append in result
    return result;

Also make sure the method is available in FunkyNumbers class. If not accessible there, then move/copy there.

Sam I am says Reinstate Monica · Answer 2 · 2012-11-07T21:44:43.210

1

try

        result += numbers[i] + "\t";

in your ToString() method

Include the code to your FunkyNumbers class and i might be able to provide better feedback.

edited Nov 07 '12 at 21:44

answered Nov 07 '12 at 21:39

Sam I am says Reinstate Monica

30,851
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3

That will not affect the output, as OP is printing instance of some `FunkyNumbers` class. – Rohit Jain Nov 07 '12 at 21:40
@RohitJain maybe FunkyNumber extends Example, – Sam I am says Reinstate Monica Nov 07 '12 at 21:41
1

@SamIam thats a big mayb.. :P – PermGenError Nov 07 '12 at 21:42
well that certainly helped, but I'm still slightly off. I get – user1804737 Nov 07 '12 at 21:44
@user1804737 I bet you tried to create a new line in your comment, didn't you? It's normally best to edit the question. – Sam I am says Reinstate Monica Nov 07 '12 at 21:45

tim_a · Answer 3 · 2012-11-07T21:54:40.573

An array in java is an object. So the variable funNumbers has as value not the array but a reference which points to the address in your memory where the array is located. When you use toString() you print this memory address on your screen and not the array as a String. You should use a StringBuffer instead to "convert" the array to a String.

private static String convertArrayToString(int[] a) {
        StringBuffer sb = new StringBuffer();
        for(int i=0; i<a.length; i++)
            sb.append(a[i]);
        return sb.toString();
    }

You can also use Arrays.toString(arg) to "convert" your array to a String. As argument you give your array and you get a String representation of your array back. If your array is multidimensional use Arrays.deepToString(arg) instead.

My program is not computing the right output, and I'm not sure why

3 Answers3