Data Structures and Algorithms in Java[1].pdf - Fulvio Frisone

In this example, notice that the class definition is delimited by braces, that is, it
begins with a "{" and ends with a "} ". In Java, any set of statements between the
braces "{" and "}" define a program block.
As with the Universe class, the Counter class is public, which means that any other
class can create and use a Counter object. The Counter has one instance variable—
an integer called count. This variable is initialized to 0 in the constructor method,
Counter, which is called when we wish to create a new Counter object (this method
always has the same name as the class it belongs to). This class also has one
accessor method, getCount, which returns the current value of the counter. Finally,
this class has two update methods—a method, incrementCount, which increments
the counter, and a method, decrementCount, which decrements the counter.
Admittedly, this is a pretty boring class, but at least it shows us the syntax and
structure of a Java class. It also shows us that a Java class does not have to have a
main method (but such a class can do nothing by itself).
The name of a class, method, or variable in Java is called an identifier, which can be
any string of characters as long as it begins with a letter and consists of letters,
numbers, and underscore characters (where "letter" and "number" can be from any
written language defined in the Unicode character set). We list the exceptions to
this general rule for Java identifiers in Table 1.1.
Table 1.1: A listing of the reserved words in Java.
These names cannot be used as method or variable
names in Java.
Reserved Words
abstract
18