Changing the JRE being used in Eclipse

To change the JRE you are currently working on

• Window > Preferences > Java >Installed JREs
• Add the new installed JRE. Check the one you want to use.
• Now go to Window > Preferences > Java > Compiler
• change the "Compiler compliance level" to the one you are using

To fix the JRE not compatible with workspace .class file compatibility: 1.6 error

• Window > Preferences > Java > Compiler and change the "Compiler compliance level" to 5.0