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JEP 221 may affect code that uses the Doclet API. It replaces the Doclet API with a simpler design that leverages newer alternative APIs with improved functionality, and updates the standard doclet to use it.
Validate JVM Command-Line Flag Arguments
JEP 245 may affect code that passes invalid flag arguments to the JVM. It validates the arguments to all JVM command-line flags so as to avoid crashes, and ensured that appropriate error messages are displayed when they are invalid.
New JDK 9 features
REPL (aka Project Kulla)
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Overview
Content Tools
ThemeBuilder