question: private void checkCyclicSubstitution ( final String varName , final List < String > priorVariables ) { if ( priorVariables . contains ( varName ) == false ) { return ; } final StrBuilder buf = new StrBuilder ( 256 ) ; buf . append ( "Infinite loop in property interpolation of " ) ; buf . append ( priorVariables . remove ( 0 ) ) ; buf . append ( ": " ) ; buf . appendWithSeparators ( priorVariables , "->" ) ; throw new IllegalStateException ( buf . toString ( ) ) ; }
target:  Checks if the specified variable is already in the stack (list) of variables.