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JDK Version Integrity


This essay does not describe an existing computer program, just one that should exist. This essay is about a suggested student project in Java programming. This essay gives a rough overview of how it might work. I have no source, object, specifications, file layouts or anything else useful to implementing this project. Everything I have prepared to help you is right here.

This project outline is not like the artificial, tidy little problems you are spoon-fed in school, when all the facts you need are included, nothing extraneous is mentioned, the answer is fully specified, along with hints to nudge you toward a single expected canonical solution. This project is much more like the real world of messy problems where it is up to you to fully the define the end point, or a series of ever more difficult versions of this project and research the information yourself to solve them.

Everything I have to say to help you with this project is written below. I am not prepared to help you implement it; or give you any additional materials. I have too many other projects of my own.

Though I am a programmer by profession, I don’t do people’s homework for them. That just robs them of an education.

You have my full permission to implement this project in any way you please and to keep all the profits from your endeavour.

Please do not email me about this project without reading the disclaimer above.

If you have a Java version 1.3 installed, how can you check if the code will run on JDK (Java Development Kit) 1.1 or 1.2? You would have to install the older JDK, recompile and test. Would it not be convenient if you could just run a utility that gave a you a list of classes that you used that were not available in the older JDK. The list would tell you, " If you could avoid using these classes/methods, this code would work under version 1.1 "

How would you prepare the tables of methods available in each JDK? You would use reflection to wander through all the system jars to collect a list of classes and methods. You would need to create one such list for each JDK. You would use a similar technique to find all the user’s classes.

How would you find out what classes and methods the application uses? You have to partially disassemble the class file headers. See JASM and disassembler.

You also might modify the doclet that generates the Javadoc to ghost the entries you can’t use for a given project.

In the meantime, to prepare code for an older version of Java use:

javac.exe -source 1.4 -target 1.4 -bootclasspath C:\Program Files\Java\jre1.4.2_19\lib\rt.jar
Verify with JarCheck and test on a machine with just that Java installed.

Alternatively, keep a stable of old complete JDK ’s about and compile and test in the oldest one you want to still support your code.

JVM manager
sanity checker

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