Deleting a classpath variable

1. Open the Java > Build Path > Classpath Variables preference page.
2. Select the variable(s) you want to delete in the Defined class path variables list and click the Remove button. The variable(s) are removed from the classpath variables list on the preferences page.

Note: The reserved class path variables, JRE_LIB, JRE_SRC, and JRE_SRCROOT cannot be deleted. 

Classpath variables

Adding a variable class path entry
Attaching source to a class path variable
Creating Java elements
Defining a class path variable

Classpath Variables preference page