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From: Jan Burse <janburse@fastmail.fm>
Newsgroups: comp.lang.java.programmer
Subject: Re: Autoboxing and Performance ?
Date: Wed, 21 Aug 2013 11:54:05 +0200
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A little up in the source code one finds also:

     /**
      * Cache to support the object identity semantics of
      * autoboxing for values between -128 and 127 (inclusive)
      * as required by JLS.
      *
      * The cache is initialized on first usage.  The size of the cache
      * may be controlled by the -XX:AutoBoxCacheMax=<size> option.


> P.S.: Here is the JDK 1.7.25 source code of Integer.valueOf:
>
>     /**
>       * Returns an {@code Integer} instance representing the specified
>       * {@code int} value.  If a new {@code Integer} instance is not
>       * required, this method should generally be used in preference to
>       * the constructor {@link #Integer(int)}, as this method is likely
>       * to yield significantly better space and time performance by
>       * caching frequently requested values.
>       *
>       * This method will always cache values in the range -128 to 127,
>       * inclusive, and may cache other values outside of this range.
>       *
>       * @param  i an {@code int} value.
>       * @return an {@code Integer} instance representing {@code i}.
>       * @since  1.5
>       */
>      public static Integer valueOf(int i) {
>          assert IntegerCache.high >= 127;
>          if (i >= IntegerCache.low && i <= IntegerCache.high)
>              return IntegerCache.cache[i + (-IntegerCache.low)];
>          return new Integer(i);
>      }
>
>