public static Rule getRule ( final Stack stack ) { if ( stack . size ( ) < 1 ) { throw new IllegalArgumentException ( "Invalid NOT rule - expected one rule but received " + stack . size ( ) ) ; } Object o1 = stack . pop ( ) ; if ( o1 instanceof Rule ) { Rule p1 = ( Rule ) o1 ; return new NotRule ( p1 ) ; } throw new IllegalArgumentException ( "Invalid NOT rule: - expected rule but received " + o1 ) ; }
Create new instance from top element of stack .