MULTIDIMENSIONAL ARRAYS - Introduction to Java Programming - page 264

7.1 Introduction
Data in a table or a matrix can be represented using a two-dimensional array.

Key
Point

The preceding chapter introduced how to use one-dimensional arrays to store linear collec-
tions of elements. You can use a two-dimensional array to store a matrix or a table. For exam-
ple, the following table that lists the distances between cities can be stored using a
two-dimensional array named distances . problem

Distance Table (in miles)

Chicago Boston New York Atlanta Miami Dallas Houston

0 983 787 714 1375 967 1087

Chicago

Boston 983 0 214 1102 1763 1723 1842

New York 787 214 0 888 1549 1548 1627

Atlanta 714 1102 888 0 661 781 810

Miami 1375 1763 1549 661 0 1426 1187

Dallas 967 1723 1548 781 1426 0 239

Houston 1087 1842 1627 810 1187 239 0

double [][] distances = {
{ 0 , 983 , 787 , 714 , 1375 , 967 , 1087 },
{ 983 , 0 , 214 , 1102 , 1763 , 1723 , 1842 },
{ 787 , 214 , 0 , 888 , 1549 , 1548 , 1627 },
{ 714 , 1102 , 888 , 0 , 661 , 781 , 810 },
{ 1375 , 1763 , 1549 , 661 , 0 , 1426 , 1187 },
{ 967 , 1723 , 1548 , 781 , 1426 , 0 , 239 },
{ 1087 , 1842 , 1627 , 810 , 1187 , 239 , 0 },

};

7.2 Two-Dimensional Array Basics
An element in a two-dimensional array is accessed through a row and column index.

Key
Point

How do you declare a variable for two-dimensional arrays? How do you create a two-
dimensional array? How do you access elements in a two-dimensional array? This section
addresses these issues.

7.2.1 Declaring Variables of Two-Dimensional Arrays and Creating
Two-Dimensional Arrays
The syntax for declaring a two-dimensional array is:
elementType[][] arrayRefVar;

or

elementType arrayRefVar[][]; // Allowed, but not preferred

As an example, here is how you would declare a two-dimensional array variable matrix
of int values:
int [][] matrix;