Introduction to Classes, Objects, Methods and Strings - Java: How to Program Early Objects - page 78

Top compartment
Middle compartment

Account

- name : String
+ setName(name : String)
+ getName() : String

Bottom compartment

Fig. 3.3 | UML class diagram for class Account of Fig. 3.1.

Middle Compartment
The middle compartment contains the class's attribute name , which corresponds to the in-
stance variable of the same name in Java. Instance variable name is private in Java, so the
UML class diagram lists a minus sign ( - ) access modifier before the attribute name. Follow-
ing the attribute name are a colon and the attribute type , in this case String .

Bottom Compartment
The bottom compartment contains the class's operations , setName and getName , which
correspond to the methods of the same names in Java. The UML models operations by
listing the operation name preceded by an access modifier , in this case + getName . This plus
sign ( + ) indicates that getName is a public operation in the UML (because it's a public
method in Java). Operation getName does not have any parameters, so the parentheses fol-
lowing the operation name in the class diagram are empty , just as they are in the method's
declaration in line 16 of Fig. 3.1. Operation setName , also a public operation, has a String
parameter called name .

Return Types
The UML indicates the return type of an operation by placing a colon and the return type
after the parentheses following the operation name. Account method getName (Fig. 3.1)
has a String return type. Method setName does not return a value (because it returns void
in Java), so the UML class diagram does not specify a return type after the parentheses of
this operation.

Parameters
The UML models a parameter a bit differently from Java by listing the parameter name,
followed by a colon and the parameter type in the parentheses after the operation name.
The UML has its own data types similar to those of Java, but for simplicity, we'll use the
Java data types. Account method setName (Fig. 3.1) has a String parameter named name ,
so Fig. 3.3 lists name : String between the parentheses following the method name.

3.2.5 Additional Notes on Class AccountTest
static Method main
In Chapter 2, each class we declared had one method named main . Recall that main is a
special method that's always called automatically by the Java Virtual Machine (JVM) when
you execute an app. You must call most other methods explicitly to tell them to perform
their tasks.
Lines 7-27 of Fig. 3.2 declare method main . A key part of enabling the JVM to locate
and call method main to begin the app's execution is the static keyword (line 7), which