*
     * @return the programmatic name of this path type
     */
    @Nonnull
    String name();

    /**
     * {@return a string representation for this extensible enum describing a path type}
     * For example {@code "PathType[PATCH_MODULE:foo.bar]"}.
     */
    @Nonnull
    @Override
    String toString();

      throw new RuntimeException();
    }
  }

  static class NotInstantiable {
    private NotInstantiable() {}
  }

  private enum NoConstantEnum {}

  private enum OneConstantEnum {
    A
  }

  private enum EnumFailsToCheckNull {
    A;

    @Keep
    public void failToCheckNull(String s) {}
  }

  private interface AnInterface {}

  // methods of this class.
  private long count = 0;
  private double mean = 0.0; // any finite value will do, we only use it to multiply by zero for sum
  private double sumOfSquaresOfDeltas = 0.0;
  private double min = NaN; // any value will do
  private double max = NaN; // any value will do

  /** Adds the given value to the dataset. */
  public void add(double value) {

		&FuncExpr{},
		participle.Lexer(sqlLexer),
		participle.CaseInsensitive("Keyword"),
		participle.CaseInsensitive("Timeword"),
	)

	validCases := []string{
		"count(*)",
		"sum(2 + s.id)",
		"sum(t)",
		"avg(s.id[1])",
		"coalesce(s.id[1], 2, 2 + 3)",

		"cast(s as string)",
		"cast(s AS INT)",
		"cast(s as DECIMAL)",
		"extract(YEAR from '2018-01-09')",

* the server
* the client

* the cloud provider
* the cloud service

* the development
* the development stages

* the dict
* the dictionary
* the enumeration
* the enum
* the enum member

* the encoder
* the decoder
* to encode
* to decode

* the exception
* to raise

* the expression
* the statement

* the frontend
* the backend

            break;
        default:
            break;
        }
        return this;
    }

    /**
     * Enumeration of supported query types.
     */
    enum QueryType {
        /** Boolean query type. */
        BOOL,
        /** DisMax query type. */
        DISMAX;
    }

    /**
     * Returns the writeable name of the wrapped query builder.
     *

In this case, there are 3 query parameters:

* `needy`, a required `str`.
* `skip`, an `int` with a default value of `0`.
* `limit`, an optional `int`.

/// tip

You could also use `Enum`s the same way as with [Path Parameters](path-params.md#predefined-values){.internal-link target=_blank}.

* o servidor
* o cliente

* o provedor de nuvem
* o serviço de nuvem

* o desenvolvimento
* as etapas de desenvolvimento

* o dict
* o dicionário
* a enumeração
* o enum
* o membro do enum

* o codificador
* o decodificador
* codificar
* decodificar

* a exceção
* lançar

* a expressão
* a instrução

* o frontend
* o backend

本例中有 3 个查询参数：

* `needy`，必选的 `str` 类型参数
* `skip`，默认值为 `0` 的 `int` 类型参数
* `limit`，可选的 `int` 类型参数

/// tip | 提示

还可以像在[路径参数](path-params.md#_8){.internal-link target=_blank} 中那样使用 `Enum`。

    testComparator(ordering, 1, 12, 124, 2);
    assertEquals("Ordering.usingToString()", ordering.toString());
    assertSame(ordering, reserialize(ordering));
  }

  // use an enum to get easy serializability
  private enum CharAtFunction implements Function<String, Character> {
    AT0(0),
    AT1(1),
    AT2(2),
    AT3(3),
    AT4(4),
    AT5(5),
    ;

    final int index;