java.lang
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.
ThreadLocal()- Creates a ThreadLocal object without associating any value to it yet.
|
T | get()- Gets the value associated with the ThreadLocal object for the currently
executing Thread.
|
protected T | initialValue()- Called once per thread on the first invocation of get(), if set() was
not already called.
|
void | remove()- Removes the value associated with the ThreadLocal object for the
currently executing Thread.
|
void | set(T value)- Sets the value associated with the ThreadLocal object for the currently
executing Thread.
|
clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait |
ThreadLocal
public ThreadLocal()
Creates a ThreadLocal object without associating any value to it yet.
get
public T get()
Gets the value associated with the ThreadLocal object for the currently
executing Thread. If this is the first time the current thread has called
get(), and it has not already called set(), the value is obtained by
initialValue().
- the value of the variable in this thread
initialValue
protected T initialValue()
Called once per thread on the first invocation of get(), if set() was
not already called. The default implementation returns null.
Often, this method is overridden to create the appropriate initial object
for the current thread's view of the ThreadLocal.
- the initial value of the variable in this thread
remove
public void remove()
Removes the value associated with the ThreadLocal object for the
currently executing Thread.
set
public void set(T value)
Sets the value associated with the ThreadLocal object for the currently
executing Thread. This overrides any existing value associated with the
current Thread and prevents initialValue() from being
called if this is the first access to this ThreadLocal in this Thread.
value - the value to set this thread's view of the variable to
ThreadLocal -- a variable with a unique value per thread
Copyright (C) 2000, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
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