From 3e1b181a6785c3b77b1cd877a8f6759efad6cfe8 Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Sat, 15 Jun 2002 19:45:34 +0000 Subject: AbstractMethodError.java: Re-merged with Classpath. * java/lang/AbstractMethodError.java: Re-merged with Classpath. * java/lang/ArithmeticException.java: Likewise. * java/lang/ArrayIndexOutOfBoundsException.java: Likewise. * java/lang/ArrayStoreException.java: Likewise. * java/lang/Byte.java: Likewise. * java/lang/CharSequence.java: Likewise. * java/lang/ClassCastException.java: Likewise. * java/lang/ClassCircularityError.java: Likewise. * java/lang/ClassFormatError.java: Likewise. * java/lang/CloneNotSupportedException.java: Likewise. * java/lang/Cloneable.java: Likewise. * java/lang/Comparable.java: Likewise. * java/lang/Compiler.java: Likewise. * java/lang/Error.java: Likewise. * java/lang/ExceptionInInitializerError.java: Likewise. * java/lang/IllegalAccessError.java: Likewise. * java/lang/IllegalAccessException.java: Likewise. * java/lang/IllegalArgumentException.java: Likewise. * java/lang/IllegalMonitorStateException.java: Likewise. * java/lang/IllegalStateException.java: Likewise. * java/lang/IllegalThreadStateException.java: Likewise. * java/lang/IncompatibleClassChangeError.java: Likewise. * java/lang/IndexOutOfBoundsException.java: Likewise. * java/lang/InheritableThreadLocal.java: Likewise. * java/lang/InstantiationError.java: Likewise. * java/lang/InstantiationException.java: Likewise. * java/lang/InternalError.java: Likewise. * java/lang/InterruptedException.java: Likewise. * java/lang/LinkageError.java: Likewise. * java/lang/NegativeArraySizeException.java: Likewise. * java/lang/NoClassDefFoundError.java: Likewise. * java/lang/NoSuchFieldError.java: Likewise. * java/lang/NoSuchFieldException.java: Likewise. * java/lang/NoSuchMethodError.java: Likewise. * java/lang/NoSuchMethodException.java: Likewise. * java/lang/NullPointerException.java: Likewise. * java/lang/NumberFormatException.java: Likewise. * java/lang/OutOfMemoryError.java: Likewise. * java/lang/Process.java: Likewise. * java/lang/Runnable.java: Likewise. * java/lang/RuntimePermission.java: Likewise. * java/lang/SecurityException.java: Likewise. * java/lang/Short.java: Likewise. * java/lang/StackOverflowError.java: Likewise. * java/lang/StringIndexOutOfBoundsException.java: Likewise. * java/lang/ThreadDeath.java: Likewise. * java/lang/ThreadLocal.java: Likewise. * java/lang/UnknownError.java: Likewise. * java/lang/UnsatisfiedLinkError.java: Likewise. * java/lang/UnsupportedClassVersionError.java: Likewise. * java/lang/UnsupportedOperationException.java: Likewise. * java/lang/VerifyError.java: Likewise. * java/lang/VirtualMachineError.java: Likewise. * java/lang/reflect/InvocationTargetException.java: Likewise. * java/net/BindException.java: Likewise. * java/net/ConnectException.java: Likewise. * java/net/MalformedURLException.java: Likewise. * java/net/NoRouteToHostException.java: Likewise. * java/net/ProtocolException.java: Likewise. * java/net/SocketException.java: Likewise. * java/net/UnknownHostException.java: Likewise. * java/net/UnknownServiceException.java: Likewise. From-SVN: r54656 --- libjava/java/lang/ThreadLocal.java | 214 +++++++++++++++++-------------------- 1 file changed, 100 insertions(+), 114 deletions(-) (limited to 'libjava/java/lang/ThreadLocal.java') diff --git a/libjava/java/lang/ThreadLocal.java b/libjava/java/lang/ThreadLocal.java index f671d4e2283..b5877f51b6a 100644 --- a/libjava/java/lang/ThreadLocal.java +++ b/libjava/java/lang/ThreadLocal.java @@ -1,5 +1,5 @@ -/* java.lang.ThreadLocal - Copyright (C) 2000 Free Software Foundation, Inc. +/* ThreadLocal -- a variable with a unique value per thread + Copyright (C) 2000, 2002 Free Software Foundation, Inc. This file is part of GNU Classpath. @@ -7,7 +7,7 @@ GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. - + GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU @@ -46,131 +46,117 @@ import java.util.WeakHashMap; * (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 (and no state is associated with that Thread yet) - * the state for that Thread is set by executing the method - * initialValue(). - *

- * An example how you can use this: + * + *

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");
- *        }
+ * 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 + * + *

When a Thread is garbage collected all references to values of * the ThreadLocal objects associated with that Thread are removed. * + * @author Mark Wielaard + * @author Eric Blake * @since 1.2 - * @author Mark Wielaard (mark@klomp.org) + * @status updated to 1.4 */ -public class ThreadLocal { - - /** - * Trivial container to wrap the stored values. - * Needed to see if the value is null or not yet set. - * If it is not yet set we must call intialValue() once. - * Package local so InheritableThreadLocal can see it. - */ - final static class Value { - final Object value; - - Value(Object value) { - this.value = value; - } - - Object getValue() { - return value; - } - } - - /** - * Maps Threads to Values. Uses a WeakHashMap so if a Thread is garbage - * collected the reference to the Value will disappear. Only the - * set(Thread, Value) and get(Thread) methods - * access it. Since this can happen from multiple Threads simultaniously - * those methods are synchronized. - */ - private final Map valueMap = new WeakHashMap(); - - /** - * Creates a ThreadLocal object without associating any value to it - * yet. - */ - public ThreadLocal() { - } - - /** - * Gets the value associated with the ThreadLocal object for the - * currently executing Thread. If there is no value is associated - * with this Thread yet then the valued returned by the - * initialValue() method is assosiated with this Thread - * and returned. - */ - public Object get() { - Thread currentThread = Thread.currentThread(); - Value v = get(currentThread); - if (v == null) { - v = new Value(initialValue()); - set(currentThread, v); - } - return v.getValue(); - } - - /** - * Gets the Value of this ThreadLocal for a particular Thread. - * It is synchronized so the set(Thread, Value) method cannot - * simultaniously modify the valueMap from another thread. - * Package local so InheritableThreadLocal can access it when a new child - * Thread inherits values from its parent Thread. - */ - synchronized final Value get(Thread thread) { - return (Value)valueMap.get(thread); - } - - /** - * Sets the value associated with the ThreadLocal object for the - * currently executing Thread. This overrides any existing value - * associated with the current Thread and does not call the - * initialValue() method, even if this is the first - * time this Thread accesses this ThreadLocal. - */ - public void set(Object value) { - Thread currentThread = Thread.currentThread(); - Value v = new Value(value); - set(currentThread, v); - } +public class ThreadLocal +{ + /** + * Placeholder to distinguish between uninitialized and null set by the + * user. Do not expose this to the public. Package visible for use by + * InheritableThreadLocal + */ + static final Object NULL = new Object(); + + /** + * The stored value. Package visible for use by InheritableThreadLocal. */ + Object value; - /** - * Sets the Value for this ThreadLocal for a particular Thread. - * It is synchronized so the get(Thread) method cannot - * simultaniously read the valueMap from another thread. - * Package local so InheritableThreadLocal can access it when a new child - * Thread inherits values from its parent Thread. - */ - synchronized final void set(Thread thread, Value value) { - valueMap.put(thread, value); - } + /** + * Maps Threads to values. Uses a WeakHashMap so if a Thread is garbage + * collected the reference to the Value will disappear. A null value means + * uninitialized, while NULL means a user-specified null. Only the + * set(Thread, Object) and get(Thread) methods + * access it. Package visible for use by InheritableThreadLocal. + */ + final Map valueMap = new WeakHashMap(); - /** - * Called when get() is called and no state is associated - * with the currently executing Thread yet. - *

- * The default implementation returns null. - */ - protected Object initialValue() { - return null; - } + /** + * Creates a ThreadLocal object without associating any value to it yet. + */ + public ThreadLocal() + { + } + + /** + * 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. + * + * @return the initial value of the variable in this thread + */ + protected Object initialValue() + { + return null; + } + + /** + * 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(). + * + * @return the value of the variable in this thread + */ + public Object get() + { + Thread currentThread = Thread.currentThread(); + // Note that we don't have to synchronize, as only this thread will + // ever modify the returned value. + Object value = valueMap.get(currentThread); + if (value == null) + { + value = initialValue(); + valueMap.put(currentThread, value == null ? NULL : value); + } + return value == NULL ? null : 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. + * + * @param value the value to set this thread's view of the variable to + */ + public void set(Object value) + { + // Note that we don't have to synchronize, as only this thread will + // ever modify the returned value. + valueMap.put(Thread.currentThread(), value == null ? NULL : value); + } } -- cgit v1.2.3