Class TypeVisitor

output/java_guava/1.4.17/TypeVisitor.java:58–112

Based on what a Type is, dispatch it to the corresponding visit method. By default, no recursion is done for type arguments or type bounds. But subclasses can opt to do recursion by calling #visit for any Type while visitation is in progress. For example, this can be

@NotThreadSafe
abstract class TypeVisitor {
  private final Set<Type> visited = Sets.newHashSet();

  /**
   * Visits the given types. Null types are ignored. This allows subclasses to call
   * {@code visit(parameterizedType.getOwnerType())} safely without having to check nulls.
   */


  public final void visit(Type... types) {
    for (Type type : types) {
      if (type == null || !visited.add(type)) {
        // null owner type, or already visited;
        continue;
      }
      boolean succeeded = false;
      try {
        if (type instanceof TypeVariable) {
          visitTypeVariable((TypeVariable<?>) type);
        } else if (type instanceof WildcardType) {
          visitWildcardType((WildcardType) type);
        } else if (type instanceof ParameterizedType) {
          visitParameterizedType((ParameterizedType) type);
        } else if (type instanceof Class) {
          visitClass((Class<?>) type);
        } else if (type instanceof GenericArrayType) {
          visitGenericArrayType((GenericArrayType) type);
               } else {
                 throw new AssertionError("Unknown type: " + type);
               }
        succeeded = true;
      } finally {
        if (!succeeded) { // When the visitation failed, we don't want to ignore the second.
          visited.remove(type);
        }
      }
    }
  }


  void visitClass(Class<?> t) {}


  void visitGenericArrayType(GenericArrayType t) {}


  void visitParameterizedType(ParameterizedType t) {}


  void visitTypeVariable(TypeVariable<?> t) {}


  void visitWildcardType(WildcardType t) {}
}