Basic Java Learning 10

Two-dimensional arrays

The array is a reference data type, and the default value is null.

Defines a one-dimensional array in the form of:int[] i = new int[];

It can be seen that each element of a one-dimensional array is an int, then the two-dimensional array is originally each element is now changed to every array, that is, int[].

So the definition of a two-dimensional array is:

int[] [] i = new int [4][5];//red indicates second dimension

The structure of the two-dimensional array in memory:

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Exceptions in the array:

1 array subscript out of bounds: java.lang.ArrayIndexOutOfBoundsException

int[] i = new int[3];

for (int m = 0;m <= i.length;m++)

{

System.out.println (I[m]);

}

2 exception for null pointer: java.lang.NullPointerException

(1)

boolean[] i = new boolean[3];

i = null;

System.out.println (I[0]);

(2)

string[] str = new STRING[3];

System.out.println (Str[0]);

(3)

Int[][] J = new int[3][];

J[2][1] = 8;

System.out.println (j[2][1]);

Basic Java Learning 10