Choosing a JRE for a launch configuration

Instead of using the default JRE for running and debugging all Java Application launch configurations, you can specifically assign a JRE for launching an individual configuration.

1. With a Java Application configuration selected in the Launch Configuration Dialog, select the JRE tab.
2. In the list of available JREs, select the JRE you want to use to launch this configuration and click Apply, then Run or Debug.

Note: Changing the JRE used for running does not affect the way Java source is compiled. You can adjust the build path to compile against custom libraries. 

Java development tools (JDT)

Working with JREs
Adding a new JRE definition
Deleting a JRE definition
Choosing a default JRE

Installed JREs preference page