code: public DateTimePatternGenerator addPattern(String pattern, boolean override, PatternInfo returnInfo) {
          return addPatternWithSkeleton(pattern, null, override, returnInfo);
      }
docs: Adds a pattern to the generator. If the pattern has the same skeleton as
  an existing pattern, and the override parameter is set, then the previous
  value is overridden. Otherwise, the previous value is retained. In either
  case, the conflicting information is returned in PatternInfo.
  <p>
  Note that single-field patterns (like "MMM") are automatically added, and
  don't need to be added explicitly!
  * <p>Example code:{@sample external/icu/android_icu4j/src/samples/java/android/icu/samples/text/datetimepatterngenerator/DateTimePatternGeneratorSample.java addPatternExample}
  @param pattern Pattern to add.
  @param override When existing values are to be overridden use true, otherwise
  use false.
  @param returnInfo Returned information.