| /******************************************************************************* |
| * Copyright (c) 2007, 2008 Oracle. All rights reserved. |
| * This program and the accompanying materials are made available under the |
| * terms of the Eclipse Public License v1.0, which accompanies this distribution |
| * and is available at http://www.eclipse.org/legal/epl-v10.html. |
| * |
| * Contributors: |
| * Oracle - initial API and implementation |
| ******************************************************************************/ |
| package org.eclipse.jpt.utility.internal; |
| |
| import java.io.Serializable; |
| import java.util.EmptyStackException; |
| import org.eclipse.jpt.utility.Command; |
| |
| /** |
| * Thread-safe implementation of the Stack interface. |
| * This also provides protocol for suspending a thread until the |
| * stack is empty or not empty, with optional time-outs. |
| */ |
| public class SynchronizedStack<E> |
| implements Stack<E>, Serializable |
| { |
| /** Backing stack. */ |
| private Stack<E> stack; |
| |
| /** Object to synchronize on. */ |
| private final Object mutex; |
| |
| private static final long serialVersionUID = 1L; |
| |
| |
| // ********** constructors ********** |
| |
| /** |
| * Construct a synchronized stack that wraps the |
| * specified stack and locks on the specified mutex. |
| */ |
| public SynchronizedStack(Stack<E> stack, Object mutex) { |
| super(); |
| this.stack = stack; |
| this.mutex = mutex; |
| } |
| |
| /** |
| * Construct a synchronized stack that wraps the |
| * specified stack and locks on itself. |
| */ |
| public SynchronizedStack(Stack<E> stack) { |
| super(); |
| this.stack = stack; |
| this.mutex = this; |
| } |
| |
| /** |
| * Construct a synchronized stack that locks on the specified mutex. |
| */ |
| public SynchronizedStack(Object mutex) { |
| this(new SimpleStack<E>(), mutex); |
| } |
| |
| /** |
| * Construct a synchronized stack that locks on itself. |
| */ |
| public SynchronizedStack() { |
| this(new SimpleStack<E>()); |
| } |
| |
| |
| // ********** Stack implementation ********** |
| |
| public void push(E o) { |
| synchronized (this.mutex) { |
| this.stack.push(o); |
| this.mutex.notifyAll(); |
| } |
| } |
| |
| public E pop() { |
| synchronized (this.mutex) { |
| E o = this.stack.pop(); |
| this.mutex.notifyAll(); |
| return o; |
| } |
| } |
| |
| public E peek() { |
| synchronized (this.mutex) { |
| return this.stack.peek(); |
| } |
| } |
| |
| public boolean isEmpty() { |
| synchronized (this.mutex) { |
| return this.stack.isEmpty(); |
| } |
| } |
| |
| |
| // ********** indefinite waits ********** |
| |
| /** |
| * Suspend the current thread until the stack's empty status changes |
| * to the specified value. |
| */ |
| public void waitUntilEmptyIs(boolean empty) throws InterruptedException { |
| synchronized (this.mutex) { |
| while (this.isEmpty() != empty) { |
| this.mutex.wait(); |
| } |
| } |
| } |
| |
| /** |
| * Suspend the current thread until the stack is empty. |
| */ |
| public void waitUntilEmpty() throws InterruptedException { |
| synchronized (this.mutex) { |
| this.waitUntilEmptyIs(true); |
| } |
| } |
| |
| /** |
| * Suspend the current thread until the stack has something on it. |
| */ |
| public void waitUntilNotEmpty() throws InterruptedException { |
| synchronized (this.mutex) { |
| this.waitUntilEmptyIs(false); |
| } |
| } |
| |
| /** |
| * Suspend the current thread until the stack is empty, |
| * then "push" the specified item on to the top of the stack |
| * and continue executing. |
| */ |
| public void waitToPush(E o) throws InterruptedException { |
| synchronized (this.mutex) { |
| this.waitUntilEmpty(); |
| this.push(o); |
| } |
| } |
| |
| /** |
| * Suspend the current thread until the stack has something on it, |
| * then "pop" an item from the top of the stack and return it. |
| */ |
| public Object waitToPop() throws InterruptedException { |
| synchronized (this.mutex) { |
| this.waitUntilNotEmpty(); |
| return this.pop(); |
| } |
| } |
| |
| |
| // ********** timed waits ********** |
| |
| /** |
| * Suspend the current thread until the stack's empty status changes |
| * to the specified value or the specified time-out occurs. |
| * The time-out is specified in milliseconds. Return true if the specified |
| * value was achieved; return false if a time-out occurred. |
| */ |
| public boolean waitUntilEmptyIs(boolean empty, long timeout) throws InterruptedException { |
| synchronized (this.mutex) { |
| if (timeout == 0L) { |
| this.waitUntilEmptyIs(empty); // wait indefinitely until notified |
| return true; // if it ever comes back, the condition was met |
| } |
| |
| long stop = System.currentTimeMillis() + timeout; |
| long remaining = timeout; |
| while ((this.isEmpty() != empty) && (remaining > 0L)) { |
| this.mutex.wait(remaining); |
| remaining = stop - System.currentTimeMillis(); |
| } |
| return (this.isEmpty() == empty); |
| } |
| } |
| |
| /** |
| * Suspend the current thread until the stack is empty |
| * or the specified time-out occurs. |
| * The time-out is specified in milliseconds. Return true if |
| * the stack is empty; return false if a time-out occurred. |
| */ |
| public boolean waitUntilEmpty(long timeout) throws InterruptedException { |
| synchronized (this.mutex) { |
| return this.waitUntilEmptyIs(true, timeout); |
| } |
| } |
| |
| /** |
| * Suspend the current thread until the stack has something on it. |
| * or the specified time-out occurs. |
| * The time-out is specified in milliseconds. Return true if |
| * the stack has something on it; return false if a time-out occurred. |
| */ |
| public boolean waitUntilNotEmpty(long timeout) throws InterruptedException { |
| synchronized (this.mutex) { |
| return this.waitUntilEmptyIs(false, timeout); |
| } |
| } |
| |
| /** |
| * Suspend the current thread until the stack is empty, |
| * then "push" the specified item on to the top of the stack |
| * and continue executing. If the stack is not emptied out |
| * before the time-out, simply continue executing without |
| * "pushing" the item. |
| * The time-out is specified in milliseconds. Return true if the |
| * item was pushed; return false if a time-out occurred. |
| */ |
| public boolean waitToPush(E o, long timeout) throws InterruptedException { |
| synchronized (this.mutex) { |
| boolean success = this.waitUntilEmpty(timeout); |
| if (success) { |
| this.push(o); |
| } |
| return success; |
| } |
| } |
| |
| /** |
| * Suspend the current thread until the stack has something on it, |
| * then "pop" an item from the top of the stack and return it. |
| * If the stack is empty and nothing is "pushed" on to it before the |
| * time-out, throw an empty stack exception. |
| * The time-out is specified in milliseconds. |
| */ |
| public Object waitToPop(long timeout) throws InterruptedException { |
| synchronized (this.mutex) { |
| boolean success = this.waitUntilNotEmpty(timeout); |
| if (success) { |
| return this.pop(); |
| } |
| throw new EmptyStackException(); |
| } |
| } |
| |
| |
| // ********** synchronized behavior ********** |
| |
| /** |
| * If the current thread is not interrupted, execute the specified command |
| * with the mutex locked. This is useful for initializing the stack in another |
| * thread. |
| */ |
| public void execute(Command command) throws InterruptedException { |
| if (Thread.interrupted()) { |
| throw new InterruptedException(); |
| } |
| synchronized (this.mutex) { |
| command.execute(); |
| } |
| } |
| |
| |
| // ********** additional public protocol ********** |
| |
| /** |
| * Return the object this object locks on while performing |
| * its operations. |
| */ |
| public Object mutex() { |
| return this.mutex; |
| } |
| |
| |
| // ********** Object overrides ********** |
| |
| @Override |
| public String toString() { |
| synchronized (this.mutex) { |
| return this.stack.toString(); |
| } |
| } |
| |
| } |