From dougo@ccs.neu.edu Tue Dec  2 17:46:34 1997
From: Doug Orleans <dougo@ccs.neu.edu>
To: ldodds@draper.com
Cc: lieber@ccs.neu.edu, binoy@ccs.neu.edu, jayantha@ccs.neu.edu,
        johan@ccs.neu.edu, kedar@ccs.neu.edu, ldodds@draper.com,
        mira@ccs.neu.edu
Subject: Re: limited memory

 > >I have a few questions:
 > >-  What to do about limited memory.  I cannot read in more than 40-50
 > >classes at a time.

See the manual for the java tool
(http://www.javasoft.com/products/jdk/1.1/docs/tooldocs/solaris/java.html).
In particular, look at the -mx option.  demjava itself uses -mx32m.

--Doug

From ldodds@ccs.neu.edu Tue Dec  2 22:01:45 1997
cc: Karl Lieberherr <lieber@ccs.neu.edu>
Subject: Memory and java class interface questions

Doug,

I spoke with Prof Lieberherr and he told me to foward these questions to
you.

I am working on a project to pasre java files and calculate a series of
metrics. For some of the metrics I need a collection of Java files.  In
order to maintain a collection of java files I have added a class to the
java.cd file (the one from Binoy) that contains a list of CompilationUnit.
This new class is marked noparse.  In the beh file I parse each file using
the CompilationUnit.  Then I add the CompilationUnit to the list of Units
by excuting:
	javaSystem.addElement(unit);
where javaSystem is the object of the CompilationUnits and unit the class
return from the freshly parsed CompilationUnit.

My problem is that because the CompilationUnit is so large, I cannot parse
more the 50 files before the virtual machine runs out of memory.  Is there
anything EASY I can do to solve this problem?  I though about serializing
the objects and storing them to disk until I need them but that will be
rather involved.  Can I add more memory to the virtual machine (hack!)?

My other problem is dealing with calculating the violations of LoD. When a
statement like the following is executed:
	H  h = a.b().c();

The problem is that I would normally look up the b() method and determine
the type of object that it returns so I could determine if the c() call is
a violation.  However, in Java, the b() could return a class that is not
in the Java system I am parsing or worse is not available to me in any
way.  For example what if b() returns a class that is in java.io or
java.util.  I this case, I have no access to the interface without parsing
the .class file.  This problem obviously continues with longer chains. 
Does that seem right? Is there anything I can do?
Larry


From dougo@ccs.neu.edu Tue Dec  2 22:21:50 1997

Larry Dodds writes:
 > I spoke with Prof Lieberherr and he told me to foward these questions to
 > you.

I already sent you mail, but it may have been to your other address.

 > Can I add more memory to the virtual machine (hack!)?

Yep, it's a command-line argument to the "java" program: -mx32m will
give it 32 megs of heap to work with (that's what I use for demjava
itself). 

 > My other problem is dealing with calculating the violations of LoD. When a
 > statement like the following is executed:
 > 	H  h = a.b().c();
 > 
 > The problem is that I would normally look up the b() method and determine
 > the type of object that it returns so I could determine if the c() call is
 > a violation.  However, in Java, the b() could return a class that is not
 > in the Java system I am parsing or worse is not available to me in any
 > way.  For example what if b() returns a class that is in java.io or
 > java.util.  I this case, I have no access to the interface without parsing
 > the .class file.

Demeter considers all external classes (i.e. those not in the class
dictionary) to be terminal classes.  Thus you shouldn't need to know
what methods are on them.

 > This problem obviously continues with longer chains. 

Any chain longer than 1 is a violation, isn't it?

--Doug