Combine Access Rules

Access rules that can added to build classpath entries to specify which types in the given entry can be accessed and which not, can be combined with the access rules that are specified for the exported build path entries of the required project by checking the checkbox Combine rules with the access rules of the exported project entries in the Type Access Rules dialog. If unchecked, only the rules given in the dialog are applied.

Access Rules
Java builder
Classpath variable
Inclusion and exclusion patterns Java build path properties
Error/Warningspreference page