I've been playing with SA4J a Structural Analysis Package for Java by IBM. This package helps with the analysis and maintenance of legacy systems, as well as helping to improve existing designs.

One real benefit of the package it helps unroll complex inter-dependancies between objects. Sometimes these "tangles" are not always easily noticable looking at the code. Just over time the system does not scale.

It identifies structural patterns in the system that hinder maintenance over time:

Tangled

A tangle is a large group of objects whose relationships are so interconnected that a change in any one of them could affect all of the others. Long tangles are a major cause of instability in large systems.

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Recently I've done a job where I needed to sign an applet. I got unstuck as some of the jars had inadvertantly got signed with the incorrect signature. However I quite quickly discovered that all the data containing the signatures and the certificate are in the meta-data of the jar. To remove a signature on a jar you can un-jar it, and remove the meta-data portion of the jar (the META-INF directory) and then jar it back up. So in unix it would be something like:

mkdir tmp
cd tmp
jar xvf ../foo.jar
rm -rf META-INF
jar cvf ../foo.jar *

I've just remembered two, perhaps rhetorical, questions that I was once asked:

1. How can ever Java be faster than native code when it runs in a virtual machine?
2. When I miss a semicolon of the end of a compilation line, why doesn't it just insert the semi-colon and continue? If it knows what's wrong with it, it should just fix it?