Class Types

guava/src/com/google/common/reflect/Types.java:54–700

Utilities for working with {@link Type}. @author Ben Yu

 * @author Ben Yu
 */
final class Types {

  /** Class#toString without the "class " and "interface " prefixes */
  private static final Joiner COMMA_JOINER = Joiner.on(", ").useForNull("null");

  /** Returns the array type of {@code componentType}. */
  static Type newArrayType(Type componentType) {
    if (componentType instanceof WildcardType) {
      WildcardType wildcard = (WildcardType) componentType;
      Type[] lowerBounds = wildcard.getLowerBounds();
      checkArgument(lowerBounds.length <= 1, "Wildcard cannot have more than one lower bounds.");
      if (lowerBounds.length == 1) {
        return supertypeOf(newArrayType(lowerBounds[0]));
      } else {
        Type[] upperBounds = wildcard.getUpperBounds();
        checkArgument(upperBounds.length == 1, "Wildcard should have only one upper bound.");
        return subtypeOf(newArrayType(upperBounds[0]));
      }
    }
    return JavaVersion.CURRENT.newArrayType(componentType);
  }

  /**
   * Returns a type where {@code rawType} is parameterized by {@code arguments} and is owned by
   * {@code ownerType}.
   */
  static ParameterizedType newParameterizedTypeWithOwner(
      @Nullable Type ownerType, Class<?> rawType, Type... arguments) {
    if (ownerType == null) {
      return newParameterizedType(rawType, arguments);
    }
    // ParameterizedTypeImpl constructor already checks, but we want to throw NPE before IAE
    checkNotNull(arguments);
    checkArgument(rawType.getEnclosingClass() != null, "Owner type for unenclosed %s", rawType);
    return new ParameterizedTypeImpl(ownerType, rawType, arguments);
  }

  /** Returns a type where {@code rawType} is parameterized by {@code arguments}. */
  static ParameterizedType newParameterizedType(Class<?> rawType, Type... arguments) {
    return new ParameterizedTypeImpl(
        ClassOwnership.JVM_BEHAVIOR.getOwnerType(rawType), rawType, arguments);
  }

  /** Decides what owner type to use for constructing {@link ParameterizedType} from a raw class. */
  private enum ClassOwnership {
    OWNED_BY_ENCLOSING_CLASS {
      @Override
      @Nullable Class<?> getOwnerType(Class<?> rawType) {
        return rawType.getEnclosingClass();
      }
    },
    LOCAL_CLASS_HAS_NO_OWNER {
      @Override
      @Nullable Class<?> getOwnerType(Class<?> rawType) {
        if (rawType.isLocalClass()) {
          return null;
        } else {
          return rawType.getEnclosingClass();