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

*** 40,49 ****
--- 40,50 ----
  import java.util.regex.Pattern;
  import java.util.regex.PatternSyntaxException;
  import java.util.stream.IntStream;
  import java.util.stream.StreamSupport;
  import jdk.internal.HotSpotIntrinsicCandidate;
+ import jdk.internal.vm.annotation.Stable;
  
  /**
   * The {@code String} class represents character strings. All
   * string literals in Java programs, such as {@code "abc"}, are
   * implemented as instances of this class.
*** 117,136 ****
   */
  
  public final class String
      implements java.io.Serializable, Comparable<String>, CharSequence {
  
!     /** The value is used for character storage. */
      private final byte[] value;
  
      /**
       * The identifier of the encoding used to encode the bytes in
       * {@code value}. The supported values in this implementation are
       *
       * LATIN1
       * UTF16
       *
       */
      private final byte coder;
  
      /** Cache the hash code for the string */
      private int hash; // Default to 0
--- 118,151 ----
   */
  
  public final class String
      implements java.io.Serializable, Comparable<String>, CharSequence {
  
!     /**
!      * The value is used for character storage.
!      *
!      * @implNote This field is trusted by the VM, and is a subject to
!      * constant folding if String instance is constant. Overwriting this
!      * field after construction will cause problems.
!      *
!      * Additionally, it is marked with {@link Stable} to trust the contents
!      * of the array. No other facility in JDK provides this functionality (yet).
!      * {@link Stable} is safe here, because value is never null.
!      */
!     @Stable
      private final byte[] value;
  
      /**
       * The identifier of the encoding used to encode the bytes in
       * {@code value}. The supported values in this implementation are
       *
       * LATIN1
       * UTF16
       *
+      * @implNote This field is trusted by the VM, and is a subject to
+      * constant folding if String instance is constant. Overwriting this
+      * field after construction will cause problems.
       */
      private final byte coder;
  
      /** Cache the hash code for the string */
      private int hash; // Default to 0