Java By Chetan: Java - 2-D Array Creation

To create a 2-D array or multidimensional Array we have to specify the base size of the Array.Because we are using new operator for allocating memory to array so Compulsory we should provide size at least base.For Array, creation java follows Array of Array Approach.

example 1:

If we are not Specifying the base size then we will get Compile time Error.
                                        x[ 0] =new int [2];
                                         x[1] =new int [3];

                           Memory representation of above example:

example 2:

                                           int [ ] [ ][ ] x =new int [ 3] [ ] [ ];        (valid)

In the above example, we provided the base value 3. Rest of we kept empty which is valid in java.
we won't get any compile time error or runtime exception;

example 3:

                                     int [ ] [ ] x = new int [ ] [ 2];                (invalid)

In the above example we did' provide any base value,means base index is empty so it is wrong in java.
Hence we will get Compile time Error.

Que:
which of Array Declaration are valid?

int [ ] a =new int [ ];
int [ ] a =new int [ 3];
int [ ] [ ] a =new int [ ] [ ];
int [ ] [ ]a =new int [ 2] [ ];
int [ ] [ ]a =new int [ ] [ 4];
int [ ] [ ]a =new int [ 2] [3 ];
int [ ] [ ] [ ]a =new int [ 2] [ 4] [ 5];
int [ ] [ ] [ ]a =new int [ ] [ 1] [2 ];
int [ ] [ ] [ ]a =new int [ 2] [ ] [3 ];

Now scroll down for check your answers;

Ans

int [ ] a =new int [ ];                   (invalid)
int [ ] a =new int [ 3];                  (valid)
int [ ] [ ] a =new int [ ] [ ];   (invalid)
int [ ] [ ]a =new int [ 2] [ ];           (valid)
int [ ] [ ]a =new int [ ] [ 4];    (invalid)
int [ ] [ ]a =new int [ 2] [3 ];          (valid)
int [ ] [ ] [ ]a =new int [ 2] [ 4] [ 5];       (valid)
int [ ] [ ] [ ]a =new int [ 2] [ 4] [ 3];       (valid)
int [ ] [ ] [ ]a =new int [ ] [ 1] [2 ];    (invalid)
int [ ] [ ] [ ]a =new int [ 2] [ ] [3 ];        (valid)