public static <K, V> NavigableMap<K, V> synchronizedNavigableMap (NavigableMap<K, V> m)

Returns a synchronized (thread-safe) navigable map backed by the specified navigable map. In order to guarantee serial access, it is critical that all access to the backing navigable map is accomplished through the returned navigable map (or its views).

It is imperative that the user manually synchronize on the returned navigable map when traversing any of its collection views, or the collections views of any of its subMap, headMap or tailMap views, via Iterator, Spliterator or Stream:

  NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
      ...
  Set s = m.keySet();  // Needn't be in synchronized block
      ...
  synchronized (m) {  // Synchronizing on m, not s!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 

or:

  NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
  NavigableMap m2 = m.subMap(foo, true, bar, false);
      ...
  Set s2 = m2.keySet();  // Needn't be in synchronized block
      ...
  synchronized (m) {  // Synchronizing on m, not m2 or s2!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 

Failure to follow this advice may result in non-deterministic behavior.

The returned navigable map will be serializable if the specified navigable map is serializable.

Parameters:

<K>		the class of the map keys
<V>		the class of the map values
m		the navigable map to be "wrapped" in a synchronized navigable map

Returns:  a synchronized view of the specified navigable map.

Since:  1.8