Are all Java Properties' methods fully synchronized?

Question

I know that the Properties class is a sub-class of Hashtable. So all the inherited methods are synchronized, but what about the other methods of Properties such as store, load, etc? (Dealing specifically with Java 1.6)

Answer 1

I always found the doc disclaimer misleading, specially for beginners (pardon if it is not your case).

This class is thread-safe: multiple threads can share a single Properties object without the need for external synchronization.

Even Thread-safe classes need synchronization more than you think. What is synchronized on that classes are their methods, but often a user uses this classes in a more complex context.

If you only put/get it is ok, but with some more code things get tighter:

p.putProperty("k1","abc");
p.putProperty("k2","123");
String.out.println(p.get("k1")+p.get("k2"));

This example code only prints for shure "abc123" in a multi threaded environment, if the section is a synchronized block (and even then things could get wrong).

For that reason (and of courrse performance) i prefer non thread safe classes and i get forced to think: is my program thread safe ...

Answer 2

the java1.6 javadoc says:

This class is thread-safe: multiple threads can share a single Properties object without the need for external synchronization.