J%: Integrating Domain-Specific Languages with Java

J% (J-mod), is a Java language extension that supports integration with domain-specific languages (DSLs). The integration is realized through an architecture that permits external modules to support DSLs. The DSL statements can be syntactically checked at compile-time. An additional facility allows the static type checking of Java variables that appear within DSL code. To support this process each DSL module comes as a library that is used both at compile time and during program execution.