Editing a JRE definition

You can modify all settings for a JRE definition except its JRE type.

From the menu bar, select Window > Preferences.
In the left pane, expend the Java category, and select Installed JREs.
Select the JRE definition that you want to edit and click Edit.... The Edit JRE page opens.
In the JRE name field, edit the name for the JRE definition. All JREs of the same type must have a unique name.
In the JRE home directory field, edit or click Browse... to select the path to the root directory of the JRE installation (usually the directory containing the bin and lib directories for the JRE). This location is checked automatically to make sure it is a valid path.
In the Javadoc URLfield, edit or click Browse... to select the URL location. The location is used by the Javadoc export wizard as a default value and by the 'Open External Javadoc' action.
If you want to use the default libraries and source files for this JRE, select the Use default system libraries check box. Otherwise, clear it and customize as desired. Source can be attached for the referenced jars as well.
Click OK when you are done.