code: public static boolean isMethodExists(Element element, String methodName, Modifier... modifiers) {
  		if (element.getKind() != ElementKind.CLASS) {
  			throw new IllegalStateException();
  		}
  		List<Modifier> modifiersList = Arrays.asList(modifiers);
  
  		List<ExecutableElement> methods = ElementFilter.methodsIn(element.getEnclosedElements());
  		for (ExecutableElement method : methods) {
  			if (method.getSimpleName().toString().equals(methodName)
  					&& method.getModifiers().containsAll(modifiersList)) {
  				return true;
  			}
  		}
  		return false;
  	}
docs: Tests if the given element has the method with the given name.<br>
  NB: This method requires the given element has the kind of {@link ElementKind#CLASS}.<br>
  Also tests the method qualifies all of modifiers if any {@link Modifier} are also given.
  @param element
  @param methodName
  @param modifiers
  @return true if a match is found, false otherwise
  @author vvakame