Multi-dimensional array in Java - Why are errors occurring?

Question

I was writing this class for some testing purpose.

public class Crap {
    public static void main(String[] args) {
        int[][] k = new int[2][];
        k[0] = {1};
        k[1] = {2,3};
        System.out.println(k[0][0]);
        System.out.println(k[0][1]);
        System.out.println(k[1][0]);
        System.out.println(k[1][1]);
    }
}

I am getting the following error while compiling.

Crap.java:5: error: illegal start of expression
        k[0] = {1};
               ^
Crap.java:5: error: not a statement
        k[0] = {1};
                ^
Crap.java:5: error: ';' expected
        k[0] = {1};
                 ^
Crap.java:6: error: ']' expected
        k[1] = {2,3};
          ^
Crap.java:6: error: ';' expected
        k[1] = {2,3};
           ^
Crap.java:6: error: illegal start of type
        k[1] = {2,3};
             ^
Crap.java:6: error: <identifier> expected
        k[1] = {2,3};
              ^
Crap.java:6: error: ';' expected
        k[1] = {2,3};
                ^
Crap.java:6: error: illegal start of type
        k[1] = {2,3};
                 ^
Crap.java:6: error: <identifier> expected
        k[1] = {2,3};
                  ^
Crap.java:6: error: ';' expected
        k[1] = {2,3};
                   ^
Crap.java:7: error: <identifier> expected
        System.out.println(k[0][0]);
                          ^
Crap.java:7: error: ']' expected
        System.out.println(k[0][0]);
                             ^
Crap.java:7: error: ')' expected
        System.out.println(k[0][0]);
                              ^
Crap.java:7: error: ']' expected
        System.out.println(k[0][0]);
                                ^
Crap.java:7: error: illegal start of type
        System.out.println(k[0][0]);
                                 ^
Crap.java:7: error: <identifier> expected
        System.out.println(k[0][0]);
                                  ^
Crap.java:8: error: <identifier> expected
        System.out.println(k[0][1]);
                          ^
Crap.java:8: error: ']' expected
        System.out.println(k[0][1]);
                             ^
Crap.java:8: error: ')' expected
        System.out.println(k[0][1]);
                              ^
Crap.java:8: error: ']' expected
        System.out.println(k[0][1]);
                                ^
Crap.java:8: error: illegal start of type
        System.out.println(k[0][1]);
                                 ^
Crap.java:8: error: <identifier> expected
        System.out.println(k[0][1]);
                                  ^
Crap.java:9: error: <identifier> expected
        System.out.println(k[1][0]);
                          ^
Crap.java:9: error: ']' expected
        System.out.println(k[1][0]);
                             ^
Crap.java:9: error: ')' expected
        System.out.println(k[1][0]);
                              ^
Crap.java:9: error: ']' expected
        System.out.println(k[1][0]);
                                ^
Crap.java:9: error: illegal start of type
        System.out.println(k[1][0]);
                                 ^
Crap.java:9: error: <identifier> expected
        System.out.println(k[1][0]);
                                  ^
Crap.java:10: error: <identifier> expected
        System.out.println(k[1][1]);
                          ^
Crap.java:10: error: ']' expected
        System.out.println(k[1][1]);
                             ^
Crap.java:10: error: ')' expected
        System.out.println(k[1][1]);
                              ^
Crap.java:10: error: ']' expected
        System.out.println(k[1][1]);
                                ^
Crap.java:10: error: illegal start of type
        System.out.println(k[1][1]);
                                 ^
Crap.java:10: error: <identifier> expected
        System.out.println(k[1][1]);
                                  ^
Crap.java:12: error: class, interface, or enum expected
}
^

Answer 1

you need to initialize the second dimension arrays.. and the syntax is as the following:

k[0] = new int[]{1};
k[1] = new int[]{2,3};

Answer 2

Arrays in Java are objects, just not objects with a standard object syntax.

As a result, you must allocate them, and to do so you need to use the new operator.

int[] array = new int[] { 1, 4, 6, 3};

or for assigning an array to an element in a two dimensional array (as you are doing)

array[3] = new int[] { 2, 4, 6, 8 };

Also keep in mind that since they are objects, and since you are using ragged arrays, your call to de-reference the position (0,1) or (0)(1) will fail because the array at position (0) only has an item in the 0 index.

Answer 3

You cannot use in this way, that is hot java syntax is defined.

 k[0] = {1};

You can only do so while you are initializing the array, like this, for example :

 int[][] k = {{1},{2,3}};

For examples, you look here