Advice with sending a reference to another method in the same class

Question

I am working on a program for class and I am stuck. When I try to compile the following code I receive and variable not found error. please help!

public class RingBuffer 
{
    public RingBuffer(int capacity){
        double[] EmptyBuffer = new double[capacity];
        System.out.print(EmptyBuffer.length);

    }

    public int size(){
        int size = EmptyBuffer.length;
        return size;
    }

please note that I am getting an error with the size() method not being able to find the variable EmptyBuffer.

`EmptyBuffer` is a local variable to your constructor. Once the constructor finish it goes out of scope (it no longer exists). — andre, May 03 '13 at 18:36

MarioDS · Accepted Answer · 2013-05-03T18:42:49.227

3

You should probably make that a field, aka an instance variable:

public class RingBuffer 
{
    private double[] emptyBuffer;

    public RingBuffer(int capacity){
        emptyBuffer = new double[capacity];
        System.out.print(EmptyBuffer.length);
    }

    public int size(){
        int size = emptyBuffer.length;
        return size;
    }
}

This will make emptyBuffer available throughout your class, i.e. in any other method.

edited May 03 '13 at 18:42

answered May 03 '13 at 18:35

MarioDS

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by marking `emptyBuffer` in the class declaration as `static`, the problem can be secured better I guess. – Sushim Mukul Dutta May 03 '13 at 18:43
@Mario De Schaepmeester the code compiles fine with variable as a `static` , I will be glad if you can explain a bit about what will be the problem. – Sushim Mukul Dutta May 03 '13 at 18:57
1

@SushimMukulDutta You **cannot** assign a `static` (class) variable in a constructor. See [this question](http://stackoverflow.com/q/5093744/1313143). Maybe you meant `final`? – MarioDS May 03 '13 at 18:59

Brad Christie · Answer 2 · 2013-05-03T18:38:19.293

0

Pass the array as an argument to your size() method like you've done with capacity:

int size(double[] EmptyBuffer){
    int size = EmptyBuffer.length;
    return size;
}

Then:

double[] EmptyBuffer = new Double[capacity];
int size = size(EmptyBuffer); // make call to size passing the array
                              // as an argument
System.out.print(size);

edited May 03 '13 at 18:38

answered May 03 '13 at 18:32

Brad Christie

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`int size EmptyBuffer(double[] EmptyBuffer)` wtf? – MarioDS May 03 '13 at 18:37
Good catch, mis-typed. My mistake. – Brad Christie May 03 '13 at 18:38
Cleared my downvote but still I think your solution makes the fact that he made a class rather obsolete :) it's still a possibility of course. – MarioDS May 03 '13 at 18:41

Advice with sending a reference to another method in the same class

2 Answers2