From efficient Java:
Oh, and one more thing: there is a serious assessment of the effectiveness of using finalizers. On my machine, the creation and destruction time of a simple object is 5.6 ns. Adding a finalizer increases the time to 2400 ns. In other words, it is about 430 times slower to create and destroy objects with finalizers.
What makes finalizers so expensive?
http://www.ibm.com/developerworks/java/library/j-jtp01274/index.html
extract from the link above
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