Differences between JVM implementations

Question

Where do JVM Implementations differ (except licensing)? Does every JVM implement Type Erasure for the Generic handling?

Where are the differences between:

Answer 1

If the JVM claims to be Java it must pass the TCK, providing a lot of stock funcitonaltiy.

The differences are in non-core places, like garbage collection, the jconsole/visualvm in the Sun JVM, precompilation etc.

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clarification: TCK is the test suite that a virtual machine has to pass in order to be officially Java compliant.