You can install as many different Java Runtime Environments (JREs) as you like. A JRE definition consists of:
You can switch the default JRE for the workbench. The default JRE is used by default when building, running, and debugging applications.
Java development tools (JDT)
Classpath variable
Adding a new JRE definition
Assigning the default JRE for the workbench
Choosing a JRE for launching a project
Deleting a JRE definition