src/java.base/share/classes/java/util/Properties.java

*** 47,56 ****
--- 47,58 ----
  import java.util.function.Function;
  
  import jdk.internal.misc.SharedSecrets;
  import jdk.internal.util.xml.PropertiesDefaultHandler;
  
+ import jdk.internal.misc.Unsafe;
+ 
  /**
   * The {@code Properties} class represents a persistent set of
   * properties. The {@code Properties} can be saved to a stream
   * or loaded from a stream. Each key and its corresponding value in
   * the property list is a string.
*** 154,165 ****
       * Properties does not store values in its inherited Hashtable, but instead
       * in an internal ConcurrentHashMap.  Synchronization is omitted from
       * simple read operations.  Writes and bulk operations remain synchronized,
       * as in Hashtable.
       */
!     private transient ConcurrentHashMap<Object, Object> map;
  
      /**
       * Creates an empty property list with no default values.
       *
       * @implNote The initial capacity of a {@code Properties} object created
       * with this constructor is unspecified.
--- 156,170 ----
       * Properties does not store values in its inherited Hashtable, but instead
       * in an internal ConcurrentHashMap.  Synchronization is omitted from
       * simple read operations.  Writes and bulk operations remain synchronized,
       * as in Hashtable.
       */
!     private transient final ConcurrentHashMap<Object, Object> map;
  
+     private static final Unsafe UNSAFE = Unsafe.getUnsafe();
+     private static final long MAP_OFFSET
+             = UNSAFE.objectFieldOffset(Properties.class, "map");
      /**
       * Creates an empty property list with no default values.
       *
       * @implNote The initial capacity of a {@code Properties} object created
       * with this constructor is unspecified.
*** 1471,1481 ****
      protected void rehash() { /* no-op */ }
  
      @Override
      public synchronized Object clone() {
          Properties clone = (Properties) cloneHashtable();
!         clone.map = new ConcurrentHashMap<>(map);
          return clone;
      }
  
      //
      // Hashtable serialization overrides
--- 1476,1486 ----
      protected void rehash() { /* no-op */ }
  
      @Override
      public synchronized Object clone() {
          Properties clone = (Properties) cloneHashtable();
!         UNSAFE.putObjectVolatile(clone, MAP_OFFSET, new ConcurrentHashMap<>(map));
          return clone;
      }
  
      //
      // Hashtable serialization overrides
*** 1535,1549 ****
          // what is actually created.
          SharedSecrets.getJavaObjectInputStreamAccess()
                       .checkArray(s, Map.Entry[].class, HashMap.tableSizeFor((int)(elements / 0.75)));
  
          // create CHM of appropriate capacity
!         map = new ConcurrentHashMap<>(elements);
  
          // Read all the key/value objects
          for (; elements > 0; elements--) {
              Object key = s.readObject();
              Object value = s.readObject();
!             map.put(key, value);
          }
      }
  }
--- 1540,1555 ----
          // what is actually created.
          SharedSecrets.getJavaObjectInputStreamAccess()
                       .checkArray(s, Map.Entry[].class, HashMap.tableSizeFor((int)(elements / 0.75)));
  
          // create CHM of appropriate capacity
!         ConcurrentHashMap<Object,Object> tmpMap = new ConcurrentHashMap<>(elements);
  
          // Read all the key/value objects
          for (; elements > 0; elements--) {
              Object key = s.readObject();
              Object value = s.readObject();
!             tmpMap.put(key, value);
          }
+         UNSAFE.putObjectVolatile(this, MAP_OFFSET, tmpMap);
      }
  }