Creating an n-dimensional array in Java at runtime

Question

I have a String that contains arrays. Example:

"[[1, 2], [4, 5], [7, 8]]" 

Now I want to make a Java array from this. I created a function to get the dimensions and a recursive function to get each element of the array. So I have every 1-D array, but I would like to know if there is a way in Java to create a dimension array that I found at runtime? Dimension is returned as an array. For example, for the above example, the size is:

 [3, 2] 

EDIT: Is there a way to create a real array from this information? The measurement [3, 2] is just an example. I can have [3, 2, 4, 5]. Can an array be generated from this information at runtime? I do not have this information at compile time.

There is some problem, I can not comment on the answers. So, I am editing here.

Answer 1

If you are doing numerical work, you should probably use a library. For example, my Vectorz open source library provides the correct support for multidimensional arrays / matrices (with double s).

Then you can just do something like:

 INDArray m=Arrayz.parse("[[1, 2], [4, 5], [7, 8]]"); 

The INDArray object encapsulates all multidimensionality, so you don’t have to worry about writing large nested loops all the time, and it also provides many other functions and features that regular Java arrays do not have.

Answer 2

The main problem is that you cannot directly refer to the N dimensional array in the code.

Fortunately, java has a bit of a dirty hack that allows you to somehow work with N dimensional arrays:

Arrays are objects like any other non-primitive in java.

Therefore, you can have:

 // Note it Object o not Object[] o Object o = new Object [dimensionLengh]; 

You can use the recursive method to create it.

 Object createMultyDimArray(int [] dimensionLengths) { return createMultyDimArray(dimensionLengths, 0); } Object createMultyDimArray(int [] dimensionLengths, int depth) { Object [] dimension = new Object[dimensionLengths[depth]]; if (depth + 1 < dimensionLengths.length) { for (int i=0; i < dimensionLengths[depth]; i++) { dimension[i] = createMultyDimArray(dimensionLengths, depth+1); } } return dimension; } 

To use this, you need to cast from Object to Object [] .

Java is type safe on arrays and errors can cause a ClassCastException. I would recommend you also read about how to create arrays using java reflection: http://docs.oracle.com/javase/tutorial/reflect/special/arrayInstance.html .