Arrays - Building Java Programs: A Back to Basics Approach - page 468

zero-equivalent for all reference types is the special value null , which indicates “no
object”:

[0] [1] [2]

points null 3 null 3 null 3

The actual Point objects must be constructed separately with the new keyword, as
in the following code:

Point[] points = new Point[3];
points[0] = new Point(3, 7);
points[1] = new Point(4, 5);
points[2] = new Point(6, 2);

After these lines of code execute, your program will have created individual
Point objects referred to by the various array elements:

[0] [1] [2]

points

xx3 y7 x x3 4 y5 x 6 y2

Notice that the new keyword is required in four different places, because there are
four objects to be constructed: the array itself and the three individual Point objects.
You could also use the curly brace notation for initializing the array, in which case
you don't need the new keyword to construct the array itself:

Point[] points = {new Point(3, 7), new Point(4, 5), new Point(6, 2)};

Command-Line Arguments
As you've seen since Chapter 1, whenever you define a main method, you're
required to include as its parameter String[] args , which is an array of String
objects. Java itself initializes this array if the user provides what are known as
command-line arguments when invoking Java. For example, the user could exe-
cute a Java class called DoSomething from a command prompt or terminal by
using a command like:

java DoSomething

The user has the option to type extra arguments, as in the following:

java DoSomething temperature.dat temperature.out