This is the core part of Eclipse's Java development tools. It contains the non-UI support for compiling and working with Java code, including the following:
- an incremental or batch Java compiler that can run standalone or as part of the Eclipse IDE
- Java source and class file indexer and search infrastructure
- a Java source code formatter
- APIs for code assist, access to the AST and structured manipulation of Java source.
For more information, refer to the [JDT wiki page] 1 or the [JDT project overview page] 2.