Information from Software Update.
This Java for Mac OS X 10.5 Update 1 adds Java SE 6 version 1.6.0_05 to your Mac. This update does not replace the existing installation of J2SE 5.0 or change the default version of Java.
For more details on this update, visit http://docs.info.apple.com/article.html?artnum=307403
It’s lucky that this doesn’t change the default version of Java. It’s worth knowing that this is 64-bit only, which means that apps that depend on Carbon bindings in Java (using a library called SWT) will crash when you try to run them in Java 6 at the moment. So, if you install this update and then switch your default version of Java and apps start to fail or just not start, it is worth falling back to Java 5.
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