code: public Tag get(Class handlerClass) throws JspException {
          PerThreadData ptd=(PerThreadData)perThread.get();
          if( ptd!=null && ptd.current >=0 ) {
              return ptd.handlers[ptd.current--];
          } else {
  	    try {
  		return (Tag) handlerClass.newInstance();
  	    } catch (Exception e) {
  		throw new JspException(e.getMessage(), e);
  	    }
  	}
      }
docs: Gets the next available tag handler from this tag handler pool,
  instantiating one if this tag handler pool is empty.
  
  @param handlerClass Tag handler class
  
  @return Reused or newly instantiated tag handler
  
  @throws JspException if a tag handler cannot be instantiated