Summary

The Simple Source Files and Instance Main Methods JEP (formerly known as Implicitly Declared Classes and Instance Main Methods), will re-preview for JDK 24. This JEP, also introduces a simpler way of doing I/O in a program, which is more aligned with the philosophy of the JEP-to enable a smooth on-ramp to Java programming. This functionality is currently implemented in the java.io.IO class.

Problem

The Simple Source Files and Instance Main Methods feature depends on module imports, which is planned to re-preview for JDK 24. Since this JEP introduces java.io.IO, allowing this new class to be tested under real-world conditions is highly desirable.

As a consequence, we propose to re-preview Simple Source Files and Instance Main Methods for JDK 24.

Solution

The Simple Source Files and Instance Main Methods feature, and java.io.IO will re-preview for JDK 24. No significant changes are proposed under this CSR, other than small JLS improvements and clarifications. A separate change(s) to simple IO may be covered by separate CSR(s).

Specification

The current draft of the JLS is attached as "Simple Source Files and Instance main Methods (Fourth Preview) - JLS.pdf", and is also available for convenience here: https://cr.openjdk.org/~gbierman/jep495/jep495-20241024/specs/simple-source-files-instance-main-methods-jls.html

The current draft of the JVMS is attached as "Simple Source Files and Instance main Methods (Fourth Preview) - JVMS.pdf", and is also available for convenience here: https://cr.openjdk.org/~gbierman/jep495/jep495-20241024/specs/simple-source-files-instance-main-methods-jvms.html