Java 子类化枚举

方法非常简单。我想将枚举A的子类化为B，以便B继承A的所有值

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我知道这篇文章已经描述了各种解决方案（包括我的）。然而，我不认为我的最后一篇文章会在所有答案之后被阅读。因此，我发表了一篇新的帖子，给出了我的答案，希望这些解决方案能够被看到，甚至可以被使用。

我想与大家分享我的同事在子类化方面的这一优雅方法，它遵循了接口方法和其他方法

请注意，我们在这里使用自定义异常，除非用异常替换，否则此代码将无法编译

文件内容丰富，我希望你们大多数人都能理解

每个子类枚举需要实现的接口

public interface Parameter {
  /**
   * Retrieve the parameters name.
   *
   * @return the name of the parameter
   */
  String getName();

  /**
   * Retrieve the parameters type.
   *
   * @return the {@link Class} according to the type of the parameter
   */
  Class<?> getType();

  /**
   * Matches the given string with this parameters value pattern (if applicable). This helps to find
   * out if the given string is a syntactically valid candidate for this parameters value.
   *
   * @param valueStr <i>optional</i> - the string to check for
   * @return <code>true</code> in case this parameter has no pattern defined or the given string
   *         matches the defined one, <code>false</code> in case <code>valueStr</code> is
   *         <code>null</code> or an existing pattern is not matched
   */
  boolean match(final String valueStr);

  /**
   * This method works as {@link #match(String)} but throws an exception if not matched.
   *
   * @param valueStr <i>optional</i> - the string to check for
   * @throws ArgumentException with code
   *           <dl>
   *           <dt>PARAM_MISSED</dt>
   *           <dd>if <code>valueStr</code> is <code>null</code></dd>
   *           <dt>PARAM_BAD</dt>
   *           <dd>if pattern is not matched</dd>
   *           </dl>
   */
  void matchEx(final String valueStr) throws ArgumentException;

  /**
   * Parses a value for this parameter from the given string. This method honors the parameters data
   * type and potentially other criteria defining a valid value (e.g. a pattern).
   *
   * @param valueStr <i>optional</i> - the string to parse the parameter value from
   * @return the parameter value according to the parameters type (see {@link #getType()}) or
   *         <code>null</code> in case <code>valueStr</code> was <code>null</code>.
   * @throws ArgumentException in case <code>valueStr</code> is not parsable as a value for this
   *           parameter.
   */
  Object parse(final String valueStr) throws ArgumentException;

  /**
   * Converts the given value to its external form as it is accepted by {@link #parse(String)}. For
   * most (ordinary) parameters this is simply a call to {@link String#valueOf(Object)}. In case the
   * parameter types {@link Object#toString()} method does not return the external form (e.g. for
   * enumerations), this method has to be implemented accordingly.
   *
   * @param value <i>mandatory</i> - the parameters value
   * @return the external form of the parameters value, never <code>null</code>
   * @throws InternalServiceException in case the given <code>value</code> does not match
   *           {@link #getType()}
   */
  String toString(final Object value) throws InternalServiceException;
}

正在实现的枚举基类

public enum Parameters implements Parameter {
  /**
   * ANY ENUM VALUE
   */
  VALUE(new ParameterImpl<String>("VALUE", String.class, "[A-Za-z]{3,10}"));

  /**
   * The parameter wrapped by this enum constant.
   */
  private Parameter param;

  /**
   * Constructor.
   *
   * @param param <i>mandatory</i> - the value for {@link #param}
   */
  private Parameters(final Parameter param) {
    this.param = param;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public String getName() {
    return this.param.getName();
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public Class<?> getType() {
    return this.param.getType();
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public boolean match(final String valueStr) {
    return this.param.match(valueStr);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void matchEx(final String valueStr) {
    this.param.matchEx(valueStr);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public Object parse(final String valueStr) throws ArgumentException {
    return this.param.parse(valueStr);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public String toString(final Object value) throws InternalServiceException {
    return this.param.toString(value);
  }
}

public enum ExtendedParameters implements Parameter {
  /**
   * ANY ENUM VALUE
   */
  VALUE(my.package.name.VALUE);

  /**
   * EXTENDED ENUM VALUE
   */
  EXTENDED_VALUE(new ParameterImpl<String>("EXTENDED_VALUE", String.class, "[0-9A-Za-z_.-]{1,20}"));

  /**
   * The parameter wrapped by this enum constant.
   */
  private Parameter param;

  /**
   * Constructor.
   *
   * @param param <i>mandatory</i> - the value for {@link #param}
   */
  private Parameters(final Parameter param) {
    this.param = param;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public String getName() {
    return this.param.getName();
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public Class<?> getType() {
    return this.param.getType();
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public boolean match(final String valueStr) {
    return this.param.match(valueStr);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void matchEx(final String valueStr) {
    this.param.matchEx(valueStr);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public Object parse(final String valueStr) throws ArgumentException {
    return this.param.parse(valueStr);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public String toString(final Object value) throws InternalServiceException {
    return this.param.toString(value);
  }
}

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另一个问题有300多张选票。答案在那里比在这里更容易看到。那么你是在发布一个已有的问题？这正是复制品的定义。您发布的答案已经存在？为什么会这样呢？如果你喜欢这个方法，并且在另一个答案中给出了它，那就投票吧。是的，我理解你的意思。我只是在现实一点。我的答案比已经有几百票的答案更高，而且这个答案已经被标记为正确，这种可能性有多大？我自己也不一定会读到下面这么远的内容。@Dr4gon所以这都是关于积分的问题吗？@Kayaman:你真的认为拥有近三年的会员资格和100点积分，我在乎积分吗？你信不信由你决定。然而，我只是喜欢和大家分享，并开始更经常地这样做。如果这是我试图分享的反应，我不确定我是否会继续贡献。

public class ParameterImpl<T> implements Parameter {
  /**
   * The default pattern for numeric (integer, long) parameters.
   */
  private static final Pattern NUMBER_PATTERN = Pattern.compile("[0-9]+");

  /**
   * The default pattern for parameters of type boolean.
   */
  private static final Pattern BOOLEAN_PATTERN = Pattern.compile("0|1|true|false");

  /**
   * The name of the parameter, never <code>null</code>.
   */
  private final String name;

  /**
   * The data type of the parameter.
   */
  private final Class<T> type;

  /**
   * The validation pattern for the parameters values. This may be <code>null</code>.
   */
  private final Pattern validator;

  /**
   * Shortcut constructor without <code>validatorPattern</code>.
   *
   * @param name <i>mandatory</i> - the value for {@link #name}
   * @param type <i>mandatory</i> - the value for {@link #type}
   */
  public ParameterImpl(final String name, final Class<T> type) {
    this(name, type, null);
  }

  /**
   * Constructor.
   *
   * @param name <i>mandatory</i> - the value for {@link #name}
   * @param type <i>mandatory</i> - the value for {@link #type}
   * @param validatorPattern - <i>optional</i> - the pattern for {@link #validator}
   *          <dl>
   *          <dt style="margin-top:0.25cm;"><i>Note:</i>
   *          <dd>The default validation patterns {@link #NUMBER_PATTERN} or
   *          {@link #BOOLEAN_PATTERN} are applied accordingly.
   *          </dl>
   */
  public ParameterImpl(final String name, final Class<T> type, final String validatorPattern) {
    this.name = name;
    this.type = type;
    if (null != validatorPattern) {
      this.validator = Pattern.compile(validatorPattern);

    } else if (Integer.class == this.type || Long.class == this.type) {
      this.validator = NUMBER_PATTERN;
    } else if (Boolean.class == this.type) {
      this.validator = BOOLEAN_PATTERN;
    } else {
      this.validator = null;
    }
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public boolean match(final String valueStr) {
    if (null == valueStr) {
      return false;
    }
    if (null != this.validator) {
      final Matcher matcher = this.validator.matcher(valueStr);
      return matcher.matches();
    }
    return true;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void matchEx(final String valueStr) throws ArgumentException {
    if (false == this.match(valueStr)) {
      if (null == valueStr) {
        throw ArgumentException.createEx(ErrorCode.PARAM_MISSED, "The value must not be null",
            this.name);
      }
      throw ArgumentException.createEx(ErrorCode.PARAM_BAD, "The value must match the pattern: "
          + this.validator.pattern(), this.name);
    }
  }

  /**
   * Parse the parameters value from the given string value according to {@link #type}. Additional
   * the value is checked by {@link #matchEx(String)}.
   *
   * @param valueStr <i>optional</i> - the string value to parse the value from
   * @return the parsed value, may be <code>null</code>
   * @throws ArgumentException in case the parameter:
   *           <ul>
   *           <li>does not {@link #matchEx(String)} the {@link #validator}</li>
   *           <li>cannot be parsed according to {@link #type}</li>
   *           </ul>
   * @throws InternalServiceException in case the type {@link #type} cannot be handled. This is a
   *           programming error.
   */
  @Override
  public T parse(final String valueStr) throws ArgumentException, InternalServiceException {
    if (null == valueStr) {
      return null;
    }
    this.matchEx(valueStr);

    if (String.class == this.type) {
      return this.type.cast(valueStr);
    }
    if (Boolean.class == this.type) {
      return this.type.cast(Boolean.valueOf(("1".equals(valueStr)) || Boolean.valueOf(valueStr)));
    }
    try {
      if (Integer.class == this.type) {
        return this.type.cast(Integer.valueOf(valueStr));
      }
      if (Long.class == this.type) {
        return this.type.cast(Long.valueOf(valueStr));
      }
    } catch (final NumberFormatException e) {
      throw ArgumentException.createEx(ErrorCode.PARAM_BAD, "The value cannot be parsed as "
          + this.type.getSimpleName().toLowerCase() + ".", this.name);
    }

    return this.parseOther(valueStr);
  }

  /**
   * Field access for {@link #name}.
   *
   * @return the value of {@link #name}.
   */
  @Override
  public String getName() {
    return this.name;
  }

  /**
   * Field access for {@link #type}.
   *
   * @return the value of {@link #type}.
   */
  @Override
  public Class<T> getType() {
    return this.type;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public final String toString(final Object value) throws InternalServiceException {
    if (false == this.type.isAssignableFrom(value.getClass())) {
      throw new InternalServiceException(ErrorCode.PANIC,
          "Parameter.toString(): Bad type of value. Expected {0} but is {1}.", this.type.getName(),
          value.getClass().getName());
    }
    if (String.class == this.type || Integer.class == this.type || Long.class == this.type) {
      return String.valueOf(value);
    }
    if (Boolean.class == this.type) {
      return Boolean.TRUE.equals(value) ? "1" : "0";
    }

    return this.toStringOther(value);
  }

  /**
   * Parse parameter values of other (non standard types). This method is called by
   * {@link #parse(String)} in case {@link #type} is none of the supported standard types (currently
   * String, Boolean, Integer and Long). It is intended for extensions.
   * <dl>
   * <dt style="margin-top:0.25cm;"><i>Note:</i>
   * <dd>This default implementation always throws an InternalServiceException.
   * </dl>
   *
   * @param valueStr <i>mandatory</i> - the string value to parse the value from
   * @return the parsed value, may be <code>null</code>
   * @throws ArgumentException in case the parameter cannot be parsed according to {@link #type}
   * @throws InternalServiceException in case the type {@link #type} cannot be handled. This is a
   *           programming error.
   */
  protected T parseOther(final String valueStr) throws ArgumentException, InternalServiceException {
    throw new InternalServiceException(ErrorCode.PANIC,
        "ParameterImpl.parseOther(): Unsupported parameter type: " + this.type.getName());
  }

  /**
   * Convert the values of other (non standard types) to their external form. This method is called
   * by {@link #toString(Object)} in case {@link #type} is none of the supported standard types
   * (currently String, Boolean, Integer and Long). It is intended for extensions.
   * <dl>
   * <dt style="margin-top:0.25cm;"><i>Note:</i>
   * <dd>This default implementation always throws an InternalServiceException.
   * </dl>
   *
   * @param value <i>mandatory</i> - the parameters value
   * @return the external form of the parameters value, never <code>null</code>
   * @throws InternalServiceException in case the given <code>value</code> does not match
   *           {@link #getClass()}
   */
  protected String toStringOther(final Object value) throws InternalServiceException {
    throw new InternalServiceException(ErrorCode.PANIC,
        "ParameterImpl.toStringOther(): Unsupported parameter type: " + this.type.getName());
  }
}