src/java.base/share/classes/java/text/DateFormatSymbols.java

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  /*
!  * Copyright (c) 1996, 2017, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
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  /*
!  * Copyright (c) 1996, 2018, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
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          cachedHashCode = 0;
      }
  
      /**
       * Gets month strings. For example: "January", "February", etc.
+      * An array with either 12 or 13 elements will be returned depending
+      * on whether or {@link java.util.Calendar#UNDECIMBER Calendar.UNDECIMBER}
+      * is supported.
       *
       * <p>If the language requires different forms for formatting and
       * stand-alone usages, this method returns month names in the
       * formatting form. For example, the preferred month name for
       * January in the Czech language is <em>ledna</em> in the
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       * form. This method returns {@code "ledna"} in this case. Refer
       * to the <a href="http://unicode.org/reports/tr35/#Calendar_Elements">
       * Calendar Elements in the Unicode Locale Data Markup Language
       * (LDML) specification</a> for more details.
       *
+      * @implSpec This method returns 13 elements since 
+      * {@link java.util.Calendar#UNDECIMBER Calendar.UNDECIMBER} is supported.
       * @return the month strings. Use
       * {@link java.util.Calendar#JANUARY Calendar.JANUARY},
       * {@link java.util.Calendar#FEBRUARY Calendar.FEBRUARY},
       * etc. to index the result array.
       */
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          cachedHashCode = 0;
      }
  
      /**
       * Gets short month strings. For example: "Jan", "Feb", etc.
+      * An array with either 12 or 13 elements will be returned depending
+      * on whether or {@link java.util.Calendar#UNDECIMBER Calendar.UNDECIMBER}
+      * is supported.
       * 
       * <p>If the language requires different forms for formatting and
       * stand-alone usages, this method returns short month names in
       * the formatting form. For example, the preferred abbreviation
       * for January in the Catalan language is <em>de gen.</em> in the
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       * form. This method returns {@code "de gen."} in this case. Refer
       * to the <a href="http://unicode.org/reports/tr35/#Calendar_Elements">
       * Calendar Elements in the Unicode Locale Data Markup Language
       * (LDML) specification</a> for more details.
       *
+      * @implSpec This method returns 13 elements since 
+      * {@link java.util.Calendar#UNDECIMBER Calendar.UNDECIMBER} is supported.
       * @return the short month strings. Use
       * {@link java.util.Calendar#JANUARY Calendar.JANUARY},
       * {@link java.util.Calendar#FEBRUARY Calendar.FEBRUARY},
       * etc. to index the result array.
       */