Class ThreadLocal<T>

ThreadLocal objects have a different state associated with every Thread that accesses them. Every access to the ThreadLocal object (through the get() and set() methods) only affects the state of the object as seen by the currently executing Thread.

The first time a ThreadLocal object is accessed on a particular Thread, the state for that Thread's copy of the local variable is set by executing the method initialValue().

An example how you can use this:

 class Connection
 {
   private static ThreadLocal owner = new ThreadLocal()
     {
       public Object initialValue()
       {
         return("nobody");
       }
     };
 ...
 }
 

Now all instances of connection can see who the owner of the currently executing Thread is by calling owner.get(). By default any Thread would be associated with 'nobody'. But the Connection object could offer a method that changes the owner associated with the Thread on which the method was called by calling owner.put("somebody"). (Such an owner changing method should then be guarded by security checks.)

When a Thread is garbage collected all references to values of the ThreadLocal objects associated with that Thread are removed.

Since: 1.2

UNKNOWN: updated to 1.5