When you have the Java perspective open and have a Java project selected in the Package Explorer, you can create new classes in Eclipse in several ways. You can use the toolbar item with the circled C icon, you can select File→ New→ Class, or you can right-click a project in the Package Explorer and select New→ Class in the context menu. All these methods open the New Java Class dialog.
The New Java Class dialog is shown in Figure 1-9.
Over the previous few recipes, we’ve been developing
a short Java project, FirstApp
. Now
we’re going to use the following code to display a
message in that project:
public class FirstApp { public static void main(String[] args) { System.out.println("Stay cool."); } }
Creating Java classes is a fundamental skill for most Eclipse
developers, so I’m going to cover the basics here.
Note the options in this dialog: you can set a
class’s access specifier as
public
, private
, or
protected
; you
can
make the class abstract
or
final
; you can specify the
new
class’s superclass
(java.lang.Object
is the default); and you can
specify which, if any, interfaces it implements. Class creation is
covered in more detail in Chapter 3.
In this book, you’ll put examples into Java packages
to avoid any conflict with other code; here, we use packages named
after the example’s chapter, such as
org.cookbook.ch01
. Enter the name of this new
class, FirstApp
, in the Name box and the name of a
new package for this class, org.cookbook.ch01
, in
the Package box. Note in particular that under the question in this
dialog “Which method stubs would you like to
create?” that we’re leaving the
checkbox marked “public static void main(String[]
args)” checked. Doing so means that Eclipse will
create an empty main
method automatically. Click
Finish to accept the other defaults.
This creates and opens the new class, FirstApp
, as
shown in Figure 1-10. Open the
FirstApp
project in the Package Explorer, and
double-click the FirstApp.java
entry under the
org.cookbook.ch01
entry to open the new code.
You can see the code the JDT has already written in this figurenote
the package
statement that creates
the
org.cookbook.ch01
package. You also can see the
main
method Eclipse has added
to
our class. This new class will be stored in its own file,
FirstApp.java
, in the Eclipse folder
workspace\FirstApp
.
At this point, simply enter the code for this class directly in the editor and you’re set. You also can use Eclipse’s code assist to make things easier, as covered in the next recipe.
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