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?

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)

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