Do I need to uninstall Java runtime environment before installing JDK?

I have an old version of Java runtime environment. Do I need to uninstall it before installing开发者_运维知识库 new JDK?

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No, you can have many JDKs and JREs installed in parallel. Just pay attention to

1. where your PATH environment variable points to
2. what's the value of the JAVA_HOME environment variable

Here's a cross-platform reference to setting these variables (but beware, some of this may be project-specific, I just couldn't find any more canonical cross-platform document)

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JDK includes JRE, located in the (JAVA_HOME)/jre directory. If you install JDK you do not need to additionally install another JRE.