Why use parallel arrays in Java?

Question

Is there any real use case for parallel arrays in Java? It seems too cumbersome to maintain N arrays which are interrelated.

Example:

int  ages[]   = {0,          17,        2,          52,         25};
String names[] = {"None",    "Mike",    "Billy",    "Tom",      "Stan"};
int  parent[] = {0,          3,         1,          0,          3};

I can just create a class Person and store objects in one single array. Will be little more expensive, but much easy to use right?

Answer 1

The only real advantage of parallel arrays in Java is as an (IMO extreme) measure to reduce object allocation and / or heap usage. For a large enough collection of objects, 3 arrays will occupy less space AND use fewer objects than a single array of instances of some custom class.

This approach is normally a bad idea, since it makes your code a lot more fragile. Creating and using a custom class is the best approach in most situations.

Note: the Performance Tips for Android advise otherwise, but those tips are primarily focused on reducing the frequency / impact of GC pauses on user experience. And even that advice is caveated in a couple of ways.