Introduction - Java Concepts - page 26

Every Java application contains a class with a main method. When the application
starts, the instructions in the main method are executed.

The parameter String[] args is a required part of the main method. (It contains
command line arguments, which we will not discuss until Chapter 11 .) The keyword
static indicates that the main method does not operate on an object. (As you will
see in Chapter 2 , most methods in Java do operate on objects, and static methods
are not common in large Java programs. Nevertheless, main must always be static ,
because it starts running before the program can create objects.)

Each class contains definitions of methods. Each method contains a sequence of
instructions.

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20

At this time, simply consider

public class ClassName
{
public static void main(String[] args)
{
. . .
}
}

as yet another part of the Ȓplumbingȓ. Our first program has all instructions inside the
main method of a class.

The first line inside the main method is a comment

// Display a greeting in the console window

This comment is purely for the benefit of the human reader, to explain in more detail
what the next statement does. Any text enclosed between // and the end of the line is
completely ignored by the compiler. Comments are used to explain the program to
other programmers or to yourself.

Use comments to help human readers understand your program.