src/java.base/share/classes/java/lang/Byte.java

@@ -24,20 +24,21 @@
   */
  
  package java.lang;
  
  import jdk.internal.misc.CDS;
+ import jdk.internal.misc.PreviewFeatures;
+ import jdk.internal.value.DeserializeConstructor;
  import jdk.internal.vm.annotation.IntrinsicCandidate;
  import jdk.internal.vm.annotation.Stable;
  
  import java.lang.constant.Constable;
  import java.lang.constant.DynamicConstantDesc;
  import java.util.Optional;
  
  import static java.lang.constant.ConstantDescs.BSM_EXPLICIT_CAST;
  import static java.lang.constant.ConstantDescs.CD_byte;
- import static java.lang.constant.ConstantDescs.CD_int;
  import static java.lang.constant.ConstantDescs.DEFAULT_NAME;
  
  /**
   * The {@code Byte} class is the {@linkplain
   * java.lang##wrapperClass wrapper class} for values of the primitive

@@ -48,20 +49,29 @@
   * a {@code byte} to a {@code String} and a {@code String} to a {@code
   * byte}, as well as other constants and methods useful when dealing
   * with a {@code byte}.
   *
   * <p>This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
-  * class; programmers should treat instances that are
-  * {@linkplain #equals(Object) equal} as interchangeable and should not
-  * use instances for synchronization, or unpredictable behavior may
-  * occur. For example, in a future release, synchronization may fail.
+  * class; programmers should treat instances that are {@linkplain #equals(Object) equal}
+  * as interchangeable and should not use instances for synchronization, mutexes, or
+  * with {@linkplain java.lang.ref.Reference object references}.
+  *
+  * <div class="preview-block">
+  *      <div class="preview-comment">
+  *          When preview features are enabled, {@code Byte} is a {@linkplain Class#isValue value class}.
+  *          Use of value class instances for synchronization, mutexes, or with
+  *          {@linkplain java.lang.ref.Reference object references} result in
+  *          {@link IdentityException}.
+  *      </div>
+  * </div>
   *
   * @author  Nakul Saraiya
   * @author  Joseph D. Darcy
   * @see     java.lang.Number
   * @since   1.1
   */
+ @jdk.internal.MigratedValueClass
  @jdk.internal.ValueBased
  public final class Byte extends Number implements Comparable<Byte>, Constable {
  
      /**
       * A constant holding the minimum value a {@code byte} can

@@ -131,24 +141,37 @@
      }
  
      /**
       * Returns a {@code Byte} instance representing the specified
       * {@code byte} value.
-      * If a new {@code Byte} instance is not required, this method
-      * should generally be used in preference to the constructor
-      * {@link #Byte(byte)}, as this method is likely to yield
-      * significantly better space and time performance since
-      * all byte values are cached.
+      * <div class="preview-block">
+      *      <div class="preview-comment">
+      *          <p>
+      *              - When preview features are NOT enabled, {@code Byte} is an identity class.
+      *              If a new {@code Byte} instance is not required, this method
+      *              should generally be used in preference to the constructor
+      *              {@link #Byte(byte)}, as this method is likely to yield
+      *              significantly better space and time performance since
+      *              all byte values are cached.
+      *          </p>
+      *          <p>
+      *              - When preview features are enabled, {@code Byte} is a {@linkplain Class#isValue value class}.
+      *              The {@code valueOf} behavior is the same as invoking the constructor,
+      *              whether cached or not.
+      *          </p>
+      *      </div>
+      * </div>
       *
       * @param  b a byte value.
       * @return a {@code Byte} instance representing {@code b}.
       * @since  1.5
       */
      @IntrinsicCandidate
+     @DeserializeConstructor
      public static Byte valueOf(byte b) {
          final int offset = 128;
-         return ByteCache.cache[(int)b + offset];
+         return (!PreviewFeatures.isEnabled()) ? ByteCache.cache[(int)b + offset] : new Byte(b);
      }
  
      /**
       * Parses the string argument as a signed {@code byte} in the
       * radix specified by the second argument. The characters in the