code: private Collection<String> checkMethodNames(
              Collection<HttpMethodConstraintElement> methodConstraints) {
          Collection<String> methodNames = new HashSet<String>();
          for (HttpMethodConstraintElement methodConstraint :
                          methodConstraints) {
              String methodName = methodConstraint.getMethodName();
              if (!methodNames.add(methodName)) {
                  throw new IllegalArgumentException(
                      "Duplicate HTTP method name: " + methodName);
              }
          }
          return methodNames;
      }
docs: Checks for duplicate method names in methodConstraints.
  
  @param methodConstraints
  
  @retrun Set of method names
  
  @throws IllegalArgumentException if duplicate method names are
  detected