question: public boolean isValid ( ) { boolean valid = true ; if ( endtime . getTime ( ) < System . currentTimeMillis ( ) ) { valid = false ; } else if ( starttime != null ) { if ( starttime . getTime ( ) > System . currentTimeMillis ( ) ) { valid = false ; } } else { if ( authtime . getTime ( ) > System . currentTimeMillis ( ) ) { valid = false ; } } return valid ; }
target:  Checks if this credential is expired