Pointers to the same array in Java

Question

I just want to make sure I'm clear on this, as I'm not quite sure of the exact behavior. I have two arrays:

private short[] bufferA;
private short[] bufferB;

which I want to swap between. Can I do something like this:

private short[] currentBuffer;

while(something)
  {
  currentBuffer = (condition) ? bufferA : bufferB;
  modify(currentBuffer);
  }

to modify the bufferA or bufferB depending on some condition, or should I use flags and manually code it like this:

private int currentBuffer;

while(something){
  currentBuffer = (condition) ? BUFFER_A : BUFFER_B;
  if(currentBuffer == BUFFER_A) {
    modify(bufferA);
  }else{
    modify(bufferB);
  }
}

The code I'm working with is more complex than this simplified example, so if I can do it the first way that would be much preferred.

ssedano · Accepted Answer · 2011-01-04 12:28:03Z

4

Although your arrays are holding primitives, Arrays itself are objects

http://java.sun.com/docs/books/jls/second_edition/html/typesValues.doc.html#12028

so reference works ok.

Java passes by value primitives, and by reference objects.

Udo

answered Jan 4, 2011 at 12:28

ssedano

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9000 · Accepted Answer · 2011-01-04 12:24:04Z

3

Yes you can. References to arrays are like any other references.

answered Jan 4, 2011 at 12:24

9000

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Comments

Sean Reilly · Accepted Answer · 2011-01-04 12:23:40Z

2

Your first example should work fine.

answered Jan 4, 2011 at 12:23

Sean Reilly

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Sean Patrick Floyd · Accepted Answer · 2011-01-04 12:24:12Z

1

The first way will work just fine with arrays (or any other containers).

However, you can not reassign variables, just change their contents:

int myVar = someCondition ? myInt1 : myInt2;
// this has no effect on either myInt1 or myInt2
myVar = 1000;

The reason here is that Java passes everything by value, including references.

So if you pass a reference to a container somewhere else, that code can change the container's content and your code will see the changes.

answered Jan 4, 2011 at 12:24

Sean Patrick Floyd

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Dhruv Gairola · Accepted Answer · 2011-01-04 12:35:43Z

1

Both are allrite.. you can go ahead with the 1st way.. EDIT: as a side note, references in java are more like pointers in c++ than references in c++. course there still are some differences between java references and c++ pointers e.g. u can do pointer arithmetic in c++..

edited Jan 4, 2011 at 12:35

answered Jan 4, 2011 at 12:26

Dhruv Gairola

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