JVM, Class Files, and the CLEmitter - Introduction to Compiler Construction in a Java World - page 324

Instantiate CLEmitter
In order to create a class, one must create an instance of CLEmitter as the first step in
the process. All subsequent steps involve sending an appropriate message to that instance.
Each instance corresponds to a single class.
To instantiate a CLEmitter , one simply invokes its constructor:
CLEmitteroutput=newCLEmitter(true);
Change the argument to the constructor to false if only an in-memory representation of
the class is needed, in which case the class will not be written to the file system.
One then goes about adding classes, method, fields, and instructions. There are methods
for adding all of these.
Set Destination Directory for the Class
The destination directory for the class file can be set by sending to the CLEmitter instance
the following message:
publicvoiddestinationDir(StringdestDir)
where destDir is the directory where the class file will be written. If the class that is being
created specifies a package, then the class file will be written to the directory obtained by
appending the package name to the destination directory. If a destination directory is not
set explicitly, the default is \.", the current directory.
Add Class
A class can be added by sending to the CLEmitter instance the following message:
publicvoidaddClass(ArrayList<String>accessFlags,
StringthisClass,
StringsuperClass,
ArrayList<String>superInterfaces,
booleanisSynthetic)
where accessFlags 7 is a list of class access and property flags, thisClass is the name of
the class in internal form, superClass is the name of the super class in internal form,
superInterfaces is a list of direct super interfaces of the class in internal form, and
isSynthetic specifies whether the class is created by the compiler.
If the class being added is an interface, accessFlags must contain appropriate (\interac-
tive" and \abstract") modiers, superInterfaces must contain the names of the interface's
super interfaces (if any) in internal form, and superClass must always be \java/lang/Ob-
ject".
Add Inner Classes
While an inner class C is just another class and can be created using the CLEmitter interface,
the parent class P that contains the class C must be informed about C, which can be done
by sending the CLEmitter instance for P the following message:
publicvoidaddInnerClass(ArrayList<String>accessFlags,
StringinnerClass,
StringouterClass,
StringinnerName)
7 Note that the CLEmitter expects the access and property ags as String s and internally translates
them to a mask of ags. For example, \public" is translated to ACC_PUBLIC(0x0001) .