Java Reference
In-Depth Information
2. Next, method setName performs its task—that is, it assigns the name parameter's
value to instance variable name (line 12 of Fig. 3.1).
3. When program execution reaches setName 's closing right brace, it returns to where
setName was called (line 21 of Fig. 3.2), then continues at line 22 of Fig. 3.2.
The number of arguments in a method call must match the number of parameters in
the method declaration's parameter list. Also, the argument types in the method call must
be consistent with the types of the corresponding parameters in the method's declaration.
(As you'll learn in Chapter 6, an argument's type and its corresponding parameter's type
are not required to be identical .) In our example, the method call passes one argument of
type String ( theName )—and the method declaration specifies one parameter of type
String ( name , declared in line 10 of Fig. 3.1). So in this example, the type of the argument
in the method call exactly matches the type of the parameter in the method header.
Displaying the Name That Was Entered by the User
Line 22 of Fig. 3.2 outputs a blank line. When the second call to method getName (line 26)
executes, the name entered by the user in line 20 is displayed. When the statement at lines
25-26 completes execution, the end of method main is reached, so the program terminates.
3.2.3 Compiling and Executing an App with Multiple Classes
You must compile the classes in Figs. 3.1 and 3.2 before you can execute the app. This is
the first time you've created an app with multiple classes. Class AccountTest has a main
method; class Account does not. To compile this app, first change to the directory that
contains the app's source-code files. Next, type the command
javac Account.java AccountTest.java
to compile both classes at once. If the directory containing the app includes only this app's
files, you can compile both classes with the command
javac *.java
The asterisk ( * ) in *.java indicates that all files in the current directory ending with the
filename extension “ .java ” should be compiled. If both classes compile correctly—that is,
no compilation errors are displayed—you can then run the app with the command
java AccountTest
3.2.4 Account UML Class Diagram with an Instance Variable and set
and get Methods
We'll often use UML class diagrams to summarize a class's attributes and operations . In in-
dustry, UML diagrams help systems designers specify a system in a concise, graphical, pro-
gramming-language-independent manner, before programmers implement the system in
a specific programming language. Figure 3.3 presents a UML class diagram for class Ac-
count of Fig. 3.1.
Top Compartment
In the UML, each class is modeled in a class diagram as a rectangle with three compart-
ments. In this diagram the top compartment contains the class name Account centered hor-
izontally in boldface type.
 
 
 
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