First-Class Genericity for Java

Java平台已被公认为构建软件应用程序的优越工具，但它仍处于发展的早期阶段。它最严重的缺陷是一个粗糙的类型系统，它不支持泛型类型，将基本类型与对象类型分开，并且在每个对象类型中都包含空指针。因此，程序员不能在类型系统中表达许多重要的程序不变量。改进的Java类型系统可以简化许多Java程序的结构，并使程序员能够在编译时捕获更多的错误。Java平台的下一个主要版本（1.5）将支持泛型类型的受限表述。虽然这个扩展是向前迈出的重要一步，但对泛型类型使用的限制将阻止它们在许多重要的面向对象编码模式中使用。在这个项目中，我们建议设计并实现一个Java 1.5的兼容扩展，其中包含一个更高级的类型系统，在这个系统中，泛型类型可以在任何常规类型可以使用的地方使用。扩展的Java语言将使程序员能够表达重要的新数据抽象，消除大多数类型强制转换，并在编译时捕获更多错误，而不会影响程序性能。

CCR-0306494Robert CartwrightWilliam Marsh Rice UniversityThe Java platform has won acceptance as a superior vehicle for building software applications, but it is still in the early stages of evolution. Its most serious deficiency is a crude type system which does not support generic types, separates primitive types from object types, and includes the null pointer in every object type. As a result, programmers cannot express many important program invariants in the type system. An improved Java type system could simplify the structure of many Java programs and enable programmers to catch more bugs at compile time.The next major release (1.5) of the Java platform will support a restricted formulation of generic types. While this extension represents a major step forward, restrictions on the use of generic types will prevent them from being used in many important object-oriented coding patterns.In this project, we propose to design and implement a compatible extension of Java 1.5 with a more advanced type system in which generic types can be used anywhere that conventional types can. The extended Java language will enable programmers to express important new data abtractions, to eliminate most type casts, and to catch more bugs at compile time--without compromising program performance.