static boolean equals(Type a, Type b) {
    if (a == b) {
      return true; // Also handles (a == null && b == null).

    } else if (a instanceof Class) {
      return a.equals(b); // Class already specifies equals().

    } else if (a instanceof ParameterizedType) {
      if (!(b instanceof ParameterizedType)) {
        return false;
      }
      ParameterizedType pa = (ParameterizedType) a;
      ParameterizedType pb = (ParameterizedType) b;
      return equal(pa.getOwnerType(), pb.getOwnerType())
          && pa.getRawType().equals(pb.getRawType())
          && Arrays.equals(pa.getActualTypeArguments(), pb.getActualTypeArguments());

    } else if (a instanceof GenericArrayType) {
      if (!(b instanceof GenericArrayType)) {
        return false;
      }
      GenericArrayType ga = (GenericArrayType) a;
      GenericArrayType gb = (GenericArrayType) b;
      return equals(ga.getGenericComponentType(), gb.getGenericComponentType());

    } else if (a instanceof WildcardType) {
      if (!(b instanceof WildcardType)) {
        return false;
      }
      WildcardType wa = (WildcardType) a;
      WildcardType wb = (WildcardType) b;
      return Arrays.equals(wa.getUpperBounds(), wb.getUpperBounds())
          && Arrays.equals(wa.getLowerBounds(), wb.getLowerBounds());

    } else if (a instanceof TypeVariable) {
      if (!(b instanceof TypeVariable)) {
        return false;
      }
      TypeVariable<?> va = (TypeVariable<?>) a;
      TypeVariable<?> vb = (TypeVariable<?>) b;
      return va.getGenericDeclaration() == vb.getGenericDeclaration()
          && va.getName().equals(vb.getName());

    } else {
      return false; // This isn't a type we support!
    }
  }
Returns true if {@code a} and {@code b} are equal.
core/src/main/java/feign/Types.java