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Download and install the current early access from JDK9 Early Access Download. This version will be used for testing clients and for unit test runs. (And eventually for compilation). Current minimun is build 132 (check with java -version).
Also, a JDK 9 early access build 109 is required to be used as a legacy bootstrap JDK. This early access JDK is a transitional, pre-modular version of JDK 9, and will be used until OpenJFX can be modified to build with a modular version of the JDK.
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