是否可以在Java中定义一个任意的，高度嵌套的数组？

Question

In JavaScript, we can flexibly define arbitrarily, highly nested arrays. For example, the following.

var arr1 = [ [0, 1], [2, 3] ];
var arr2 = [ 
 [ [0, 1], [2, 3] ], 
 [ [4, 5], [6, 7] ] 
];

Is it possible to define something like this in Java for a field of a class? The field must be able to store arbitrary dimensions/depths of nested arrays.

I was thinking about using a List of Lists.

List<List<Integer>> arr = new ArrayList<>();

However, this is in some sense, only a 2D matrix. Note that the index is significant (it has meaning) for my use case.

I suppose I can also create a Tree structure, but that might require some non-trivial work to get it right.

public class Node {
 int index; //like the index of an array i want, unique amongst nodes of same level sharing a common parent
 List<Integer> values; //the actual elements, if any
 List<Node> children; //nesting deeper
}

Any tips are appreciated.

Answer 1

Java is a strongly typed language, you define the dimensionality of the array when you declare it. Like,

int[][] arr1 = { { 0, 1 }, { 2, 3 } };
int[][][] arr2 = { { { 0, 1 }, { 2, 3 } }, { { 4, 5 }, { 6, 7 } } };
System.out.println(Arrays.deepToString(arr2));

However, it is also possible to make an Object refer to any array (because arrays are Object instances). In the example above, note the signature is Arrays.deepToString(Object[]) .

Answer 2

1) You can do something like this (if it makes sense for you):

List<List<List<List<Integer>> arr = new ArrayList<>();

2) Also as Javascript, Java can have multi dimensional arrays

Integer[][] arr = {{1,2},{2,3}};

3) To create an Array in runtime, you can use reflection:

Integer[] array = (Integer[])Array.newInstance(Integer.class, d1);
Integer[][] array = (Integer[][])Array.newInstance(Integer.class, d1, d2);
Integer[][][] array = (Integer[][][])Array.newInstance(Integer.class, d1, d2, d3);

newInstance

4) Also you can use a library that implements multi dimensional array. Like:

Vectorz

I think the last option is the best one in your case.