A one dimensional array is an array for which you have to give a single argument (called index) to access a specific value.

E.G. with the following one dimensional array

array = [0,1,2,9,6,5,8]

The array at index 1 has the value 1. The array at index 3 has value 9. If you want to update the 3rd value to 8 in the array, you should do

array[2] = 8

A two-dimensional array is simply an array of arrays. So, you have to give two arguments to access a single value.

two_dim_array = [[1,2,3],[4,5,6],[7,8,9]]

If you want to update the 'second' value, you have to do

two_dim_array[0][1] = 'something'

That is because two_dim_array[0] is a one-dimensional array, and you still have to specify an index to access a value.

From now on, you can keep going deeper with the same reasoning. As any further dimension is another level in the list. So a three dimensional array would be :

3d_array = 
[
    [
        [1,2,3,4],
        [5,6,7,8]
    ],
    [
        [9,10,11,12],
        [13,14,15,16]
    ]
]

Now to access a value you have to give .. 3 parameters. Because

3d_array[0] // is a two-dim array
3d_array[0][1] // is a one-dim array
3d_array[0][1][0] // is a value

I suggest you start doing simple exercices to get you familiar with this concept, as it is really 101 programming stuff. W3resource has great exercices to get you started.

Making a 3D array is quite possible in Java. It's as simple as declaring the type T[][][] array;. Three separate 1D arrays are not equivalent to one 3D array. You would need n 2D arrays to be equivalent to one 3D array. The efficiency of traversing a 3D array is practically O(n³).