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

*** 24,10 ***
--- 24,11 ---
   */
  
  package java.lang;
  
  import jdk.internal.misc.CDS;
+ 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;

*** 164,26 ***
   * {@code char} values that are code units of the <em>UTF-16</em>
   * encoding. For more information on Unicode terminology, refer to the
   * <a href="http://www.unicode.org/glossary/">Unicode Glossary</a>.
   *
   * <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.
   *
   * @spec https://www.unicode.org/reports/tr27 Unicode 3.1.0
   * @author  Lee Boynton
   * @author  Guy Steele
   * @author  Akira Tanaka
   * @author  Martin Buchholz
   * @author  Ulf Zibis
   * @since   1.0
   */
  @jdk.internal.ValueBased
! public final
- class Character implements java.io.Serializable, Comparable<Character>, Constable {
      /**
       * The minimum radix available for conversion to and from strings.
       * The constant value of this field is the smallest value permitted
       * for the radix argument in radix-conversion methods such as the
       * {@code digit} method, the {@code forDigit} method, and the
--- 165,34 ---
   * {@code char} values that are code units of the <em>UTF-16</em>
   * encoding. For more information on Unicode terminology, refer to the
   * <a href="http://www.unicode.org/glossary/">Unicode Glossary</a>.
   *
   * <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, mutexes, or
!  * with {@linkplain java.lang.ref.Reference object references}.
!  *
+  * <div class="preview-block">
+  *      <div class="preview-comment">
+  *          When preview features are enabled, {@code Character} 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>
   *
   * @spec https://www.unicode.org/reports/tr27 Unicode 3.1.0
   * @author  Lee Boynton
   * @author  Guy Steele
   * @author  Akira Tanaka
   * @author  Martin Buchholz
   * @author  Ulf Zibis
   * @since   1.0
   */
+ @jdk.internal.MigratedValueClass
  @jdk.internal.ValueBased
! public final class Character implements java.io.Serializable, Comparable<Character>, Constable {
      /**
       * The minimum radix available for conversion to and from strings.
       * The constant value of this field is the smallest value permitted
       * for the radix argument in radix-conversion methods such as the
       * {@code digit} method, the {@code forDigit} method, and the

*** 9012,10 ***
--- 9021,11 ---
       * @param  c a char value.
       * @return a {@code Character} instance representing {@code c}.
       * @since  1.5
       */
      @IntrinsicCandidate
+     @DeserializeConstructor
      public static Character valueOf(char c) {
          if (c <= 127) { // must cache
              return CharacterCache.cache[(int)c];
          }
          return new Character(c);