Efficient Implementation of Run-time Generic Types for Java

摘要

We describe an efficient compiler and run-time system for NEXTGEN, a compatible extension of the Java programming language supporting run-time generic types designed by Cartwright and Steele. The resulting system is comparable in performance with both standard Java and the GJ extension of Java, which does not support run-time generic types. Our implementation of NEXTGEN consists of a compiler extending the GJ compiler and a special class loader that constructs type instantiation classes on demand. The compiler relies on the implementation strategy proposed by Cartwright and Steele with one major exception: to support polymorphic recursion in the definition of generic classes, the compiler generates templates for instantiation classes which are constructed on demand by the class loader. We include an extensive set of benchmarks, specifically developed to stress the use of generic types. The benchmarks show that the additional code required to support run-time generic types has little overhead compared with ordinary Java and GJ.