code: /*
   * Copyright (C) 2008 Google Inc.
   *
   * Licensed 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 tools.com.google.gson;
  
  import java.lang.reflect.Field;
  import java.util.Locale;
  
  /**
   * An enumeration that defines a few standard naming conventions for JSON field names.
   * This enumeration should be used in conjunction with {@link com.google.gson.GsonBuilder}
   * to configure a {@link com.google.gson.Gson} instance to properly translate Java field
   * names into the desired JSON field names.
   *
   * @author Inderjeet Singh
   * @author Joel Leitch
   */
  public enum FieldNamingPolicy implements FieldNamingStrategy {
  
    /**
     * Using this naming policy with Gson will ensure that the field name is
     * unchanged.
     */
    IDENTITY() {
      @Override public String translateName(Field f) {
        return f.getName();
      }
    },
  
    /**
     * Using this naming policy with Gson will ensure that the first "letter" of the Java
     * field name is capitalized when serialized to its JSON form.
     *
     * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p>
     * <ul>
     *   <li>someFieldName ---> SomeFieldName</li>
     *   <li>_someFieldName ---> _SomeFieldName</li>
     * </ul>
     */
    UPPER_CAMEL_CASE() {
      @Override public String translateName(Field f) {
        return upperCaseFirstLetter(f.getName());
      }
    },
  
    /**
     * Using this naming policy with Gson will ensure that the first "letter" of the Java
     * field name is capitalized when serialized to its JSON form and the words will be
     * separated by a space.
     *
     * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p>
     * <ul>
     *   <li>someFieldName ---> Some Field Name</li>
     *   <li>_someFieldName ---> _Some Field Name</li>
     * </ul>
     *
     * @since 1.4
     */
    UPPER_CAMEL_CASE_WITH_SPACES() {
      @Override public String translateName(Field f) {
        return upperCaseFirstLetter(separateCamelCase(f.getName(), " "));
      }
    },
  
    /**
     * Using this naming policy with Gson will modify the Java Field name from its camel cased
     * form to a lower case field name where each word is separated by an underscore (_).
     *
     * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p>
     * <ul>
     *   <li>someFieldName ---> some_field_name</li>
     *   <li>_someFieldName ---> _some_field_name</li>
     *   <li>aStringField ---> a_string_field</li>
     *   <li>aURL ---> a_u_r_l</li>
     * </ul>
     */
    LOWER_CASE_WITH_UNDERSCORES() {
      @Override public String translateName(Field f) {
        return separateCamelCase(f.getName(), "_").toLowerCase(Locale.ENGLISH);
      }
    },
  
    /**
     * Using this naming policy with Gson will modify the Java Field name from its camel cased
     * form to a lower case field name where each word is separated by a dash (-).
     *
     * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p>
     * <ul>
     *   <li>someFieldName ---> some-field-name</li>
     *   <li>_someFieldName ---> _some-field-name</li>
     *   <li>aStringField ---> a-string-field</li>
     *   <li>aURL ---> a-u-r-l</li>
     * </ul>
     * Using dashes in JavaScript is not recommended since dash is also used for a minus sign in
     * expressions. This requires that a field named with dashes is always accessed as a quoted
     * property like {@code myobject['my-field']}. Accessing it as an object field
     * {@code myobject.my-field} will result in an unintended javascript expression.
     * @since 1.4
     */
    LOWER_CASE_WITH_DASHES() {
      @Override public String translateName(Field f) {
        return separateCamelCase(f.getName(), "-").toLowerCase(Locale.ENGLISH);
      }
    };
  
    /**
     * Converts the field name that uses camel-case define word separation into
     * separate words that are separated by the provided {@code separatorString}.
     */
    static String separateCamelCase(String name, String separator) {
      StringBuilder translation = new StringBuilder();
      for (int i = 0, length = name.length(); i < length; i++) {
        char character = name.charAt(i);
        if (Character.isUpperCase(character) && translation.length() != 0) {
          translation.append(separator);
        }
        translation.append(character);
      }
      return translation.toString();
    }
  
    /**
     * Ensures the JSON field names begins with an upper case letter.
     */
    static String upperCaseFirstLetter(String name) {
      StringBuilder fieldNameBuilder = new StringBuilder();
      int index = 0;
      char firstCharacter = name.charAt(index);
      int length = name.length();
  
      while (index < length - 1) {
        if (Character.isLetter(firstCharacter)) {
          break;
        }
  
        fieldNameBuilder.append(firstCharacter);
        firstCharacter = name.charAt(++index);
      }
  
      if (!Character.isUpperCase(firstCharacter)) {
        String modifiedTarget = modifyString(Character.toUpperCase(firstCharacter), name, ++index);
        return fieldNameBuilder.append(modifiedTarget).toString();
      } else {
        return name;
      }
    }
  
    private static String modifyString(char firstCharacter, String srcString, int indexOfSubstring) {
      return (indexOfSubstring < srcString.length())
          ? firstCharacter + srcString.substring(indexOfSubstring)
          : String.valueOf(firstCharacter);
    }
  }
  