Java Theory and Practice: Generics Gotchas
By Brian Goetz2005-03-23
Summary
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Generics are a big step forward in the type-safety of the Java language, but the design of the generics facility, and the generification of the class library, were not without compromises. Extending the virtual machine instruction set to support generics was deemed unacceptable, because that might make it prohibitively difficult for JVM vendors to update their JVM. Accordingly, the approach of erasure, which could be implemented entirely in the compiler, was adopted. Similarly, in generifying the Java class libraries, the desire to maintain backward compatibility placed many constraints on how the class libraries could be generified, resulting in some confusing and frustrating constructions (like Array.newInstance()). These are not problems with generics per se, but with the practicality of language evolution and compatibility. But they can make generics a little more confusing, and frustrating, to learn and use.
Tutorial Pages:
» Identify and avoid some of the pitfalls in learning to use generics
» Generics are not covariant
» Construction delays
» Generifying existing classes
» Implications of erasure
» Summary
» Resources
First published by IBM developerWorks
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