content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.calcite.util.format;
  
  import org.apache.calcite.linq4j.function.Experimental;
  
  import java.util.function.Consumer;
  
  /**
   * A format element in a format string. Knows how to parse and unparse itself.
   */
  @Experimental
  public interface FormatElement {
  
    /**
     * Formats a date to its appropriate string representation for the element.
     */
    void format(StringBuilder sb, java.util.Date date);
  
    /**
     * Adds the appropriate {@link java.text.SimpleDateFormat} pattern for the element to
     * provided StringBuilder.
     *
     * <p>Note that certain FormatElements may not have a Java equivalent.
     * In such cases, calling this method will throw an {@link UnsupportedOperationException}.
     * See {@link FormatElementEnum#Q} as an example.
     */
    void toPattern(StringBuilder sb) throws UnsupportedOperationException;
  
    /**
     * Returns the description of an element.
     *
     * <p>For example, {@code %H} in MySQL represents the hour in 24-hour format
     * (e.g., 00..23). This method returns the string "The hour (24-hour clock) as
     * a decimal number (00-23)", which is the description of
     * {@link FormatElementEnum#HH24}.
     */
    String getDescription();
  
    /**
     * Applies a consumer to a format element.
     */
    default void flatten(Consumer<FormatElement> consumer) {
      consumer.accept(this);
    }
  }
  