question: public void enable ( ) { List < Entry > entries = removeIntersectedEntries ( tree . getSelectedEntries ( ) ) ; boolean enable = true ; for ( Entry entry : entries ) { if ( entry == null ) { enable = false ; break ; } if ( ! requiredSelectionType . isInstance ( entry ) ) { enable = false ; break ; } if ( needsWriteAccess && entry . isReadOnly ( ) ) { enable = false ; break ; } } if ( entries . isEmpty ( ) ) { enable = false ; } setEnabled ( enable ) ; }
target:  Enables action, if every entry exists and can be written if needed.