Question

Is there a definitive reference on this in programming?

I see a lot of people refer to deep copying and cloning as the same thing. Is this true?

Is it language dependent?

A small point, but it was bothering me…

Answer 1

Yes, there is a difference. As far as language dependencies, some languages can do all Shallow, Deep, Lazy copying. Some only do Shallow copies. So yes, it is language dependent sometimes.

Now, take for instance an Array:

int [] numbers = { 2, 3, 4, 5};
int [] numbersCopy = numbers;

The “numbersCopy” array now contains the same values, but more importantly the array object itself points to the same object reference as the “numbers” array.

So if I were to do something like:

  numbersCopy[2] = 0;
 

What would be the output for the following statements?

  System.out.println(numbers[2]);

  System.out.println(numbersCopy[2]);

Considering both arrays point to the same reference we would get:

0

0

But what if we want to make a distinct copy of the first array with its own reference? Well in that case we would want to clone the array. In doing so each array will now have its own object reference. Let’s see how that will work.

  int [] numbers = { 2, 3, 4, 5};

  int [] numbersClone = (int[])numbers.clone();

The “numbersClone” array now contains the same values, but in this case the array object itself points a different reference than the “numbers” array.

So if I were to do something like:

  numbersClone[2] = 0;

What would be the output now for the following statements?

  System.out.println(numbers[2]);

  System.out.println(numbersClone[2]);

You guessed it:

4

0

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