Java N-Dimensional Arrays

Question

I need to be able to have an n-dimensional field where n is based on an input to the constructor. But I\'m not even sure if that\'s possible. Is it?

Answer 1

Quick solution: you could approximate it with a non-generic ArrayList of ArrayList of ... going as deep as you need to. However, this may get awkward to use pretty fast.

An alternative requiring more work could be to implement your own type using an underlying flat array representation where you calculate the indexing internally, and providing accessor methods with vararg parameters. I am not sure if it is fully workable, but may be worth a try...

Rough example (not tested, no overflow checking, error handling etc. but hopefully communicates the basic idea):

class NDimensionalArray {
  private Object[] array; // internal representation of the N-dimensional array
  private int[] dimensions; // dimensions of the array
  private int[] multipliers; // used to calculate the index in the internal array

  NDimensionalArray(int... dimensions) {
    int arraySize = 1;

    multipliers = new int[dimensions.length];
    for (int idx = dimensions.length - 1; idx >= 0; idx--) {
      multipliers[idx] = arraySize;
      arraySize *= dimensions[idx];
    }
    array = new Object[arraySize];
    this.dimensions = dimensions;
  }
  ...
  public Object get(int... indices) {
    assert indices.length == dimensions.length;
    int internalIndex = 0;

    for (int idx = 0; idx < indices.length; idx++) {
      internalIndex += indices[idx] * multipliers[idx];
    }
    return array[internalIndex];
  }
  ...
}

Answer 2

Here's a nice article that explains how to use reflection to create arrays at run-time: Java Reflection: Arrays. That article explains how to create a one-dimensional array, but java.lang.reflect.Array also contains another newInstance method to create multi-dimensional arrays. For example:

int[] dimensions = { 10, 10, 10 }; // 3-dimensional array, 10 elements per dimension
Object myArray = Array.newInstance(String.class, dimensions); // 3D array of strings

Since the number of dimensions is not known until runtime, you can only handle the array as an Object and you must use the get and set methods of the Array class to manipulate the elements of the array.

Answer 3

Try this:

https://github.com/adamierymenko/hyperdrive