/** String constant representing boolean true value. */
    public static final String TRUE = "true";

    /** String constant representing boolean false value. */
    public static final String FALSE = "false";

    /** Boolean constant representing true value. */
    public static final Boolean T = true;

    /** Boolean constant representing false value. */

    assertEquals("correct", f.apply(new Object()));
    assertEquals("correct", f.apply(null));

    Function<@Nullable Object, @Nullable String> g = Functions.constant(null);
    assertEquals(null, g.apply(2));
    assertEquals(null, g.apply(null));

    new EqualsTester()
        .addEqualityGroup(f, Functions.constant("correct"))

    assertEquals("correct", f.apply(new Object()));
    assertEquals("correct", f.apply(null));

    Function<@Nullable Object, @Nullable String> g = Functions.constant(null);
    assertEquals(null, g.apply(2));
    assertEquals(null, g.apply(null));

    new EqualsTester()
        .addEqualityGroup(f, Functions.constant("correct"))

    for (MediaType constant : getConstants()) {
      assertSame(constant, MediaType.parse(constant.toString()));
    }
  }

  @J2ktIncompatible
  @GwtIncompatible // reflection
  public void testCreate_useConstants() throws Exception {
    for (MediaType constant : getConstants()) {
      assertSame(
          constant,
          MediaType.create(constant.type(), constant.subtype())

    new EqualsTester()
        .addEqualityGroup(
            Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("foo")),
            Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("foo")))
        .addEqualityGroup(Suppliers.compose(Functions.constant(2), Suppliers.ofInstance("foo")))
        .addEqualityGroup(Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("bar")))
        .testEquals();
  }

    return mediaType;
  }

  /*
   * The following constants are grouped by their type and ordered alphabetically by the constant
   * name within that type. The constant name should be a sensible identifier that is closest to the
   * "common name" of the media. This is often, but not necessarily the same as the subtype.
   *
   * Be sure to declare all constants with the type and subtype in all lowercase. For types that

        if (field.getGenericType() == field.getType() && type.isAssignableFrom(field.getType())) {
          field.setAccessible(true);
          try {
            T constant = type.cast(field.get(null));
            if (constant != null) {
              return constant;
            }
          } catch (IllegalAccessException impossible) {
            throw new AssertionError(impossible);
          }
        }
      }
    }

        if (field.getGenericType() == field.getType() && type.isAssignableFrom(field.getType())) {
          field.setAccessible(true);
          try {
            T constant = type.cast(field.get(null));
            if (constant != null) {
              return constant;
            }
          } catch (IllegalAccessException impossible) {
            throw new AssertionError(impossible);
          }
        }
      }
    }

    return mediaType;
  }

  /*
   * The following constants are grouped by their type and ordered alphabetically by the constant
   * name within that type. The constant name should be a sensible identifier that is closest to the
   * "common name" of the media. This is often, but not necessarily the same as the subtype.
   *
   * Be sure to declare all constants with the type and subtype in all lowercase. For types that

   * (Function<Object, E> & Serializable) o -> value}.
   *
   * @param value the constant value for the function to return
   * @return a function that always returns {@code value}
   */
  public static <E extends @Nullable Object> Function<@Nullable Object, E> constant(
      @ParametricNullness E value) {
    return new ConstantFunction<>(value);
  }