JEP 182: Policy for Retiring javac -source and -target Options

AuthorJoseph D. Darcy
OwnerJoe Darcy
Created2013/04/02 20:00
Updated2014/07/14 21:11
TypeInformational
StatusDraft
Componenttools / javac
ScopeJDK
Discussiondiscuss at openjdk dot java dot net
Priority4
Reviewed byBrian Goetz
Endorsed byBrian Goetz
Issue8046172

Summary

To reduce the maintenance costs of javac, this JEP defines a policy for retiring old -source and -target options. In JDK 8, use of a source or target of 1.5 or earlier will be deprecated and in JDK 9, support for a source or target of 1.5 or earlier will be removed. In JDK 9 and going forward, javac will use a "one + three back" policy of supported source and target options. Under this policy, javac will still be able to recognize and process class files of all previous JDKs, going back to version 45.3 class files generated by JDK 1.0.2, which first shipped in 1996.

Goals

Reduce compiler maintenance costs by removing obsolete code.

Motivation

By removing old source and target options, maintenance of the javac compiler is simplified. Many of the source and target values supported in JDK 8 are for release trains that have long passed their end of public updates. Users of those releases can use the javac from those releases if a recompile is necessary in the future.

The source and target options are not mandated by the Java SE specification and are provided for programmer convenience. However, maintenance of old options has nonzero cost. For example, when a -source N option older than the source level of rt.jar is specified, it is not clear how newer-than-release-N language artifacts in the platform libraries should be modeled to the code being compiled. Reducing the span of supported source and target values simplifies the design considerations of such questions.

Description

The never-documented target options jsr14, 1.4.1 and 1.4.2 have already been removed from JDK 8. Source and target values of 1.5/5 and earlier will be deprecated in JDK 8. A warning will be printed when such options are used. In JDK 9, those options will no longer be recognized by javac. JDK 9 will implement a "one plus three back" support policy meaning that 1.9/9, 1.8/8, 1.7/7, and 1.6/6 will be recognized in that release. That policy will continue in JDK 10.

Impact