Java by API/java.util.concurrent.locks/Condition

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Condition: await()

   <source lang="java">
 

/* License for Java 1.5 "Tiger": A Developer"s Notebook

    (O"Reilly) example package

Java 1.5 "Tiger": A Developer"s Notebook (O"Reilly) by Brett McLaughlin and David Flanagan. ISBN: 0-596-00738-8 You can use the examples and the source code any way you want, but please include a reference to where it comes from if you use it in your own products or services. Also note that this software is provided by the author "as is", with no expressed or implied warranties. In no event shall the author be liable for any direct or indirect damages arising in any way out of the use of this software.

  • /

import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock;

class LinkList<E> {
 // The value of this node
 E value;
 // The rest of the list
 LinkList<E> rest;

 // A lock for this node
 Lock lock;
 // Signals when the value of this node changes
 Condition valueChanged;
 // Signals when the node this is connected to changes
 Condition linkChanged;
 public LinkList(E value) {
   this.value = value;
   rest = null;
   lock = new ReentrantLock();
   valueChanged = lock.newCondition();
   linkChanged = lock.newCondition();
 }
 public void setValue(E value) {
   lock.lock();
   try {
     this.value = value;
     // Let waiting threads that the value has changed
     valueChanged.signalAll();
   } finally {
     lock.unlock();
   }
 }
 public void executeOnValue(E desiredValue, Runnable task)
   throws InterruptedException {

   lock.lock();
   try {
     // Checks the value against the desired value
     while (!value.equals(desiredValue)) {
       // This will wait until the value changes
       valueChanged.await();
     }
     // When we get here, the value is correct -- Run the task
     task.run();
   } finally {
     lock.unlock();
   }
 }
 public void append(E value) {
   // Start the pointer at this node
   LinkList<E> node = this;
   node.lock.lock();
   while (node.rest != null) {
     LinkList<E> next = node.rest;
     // Here"s the hand-over-hand locking
     try {
       // Lock the next node
       next.lock.lock();
     } finally {
       // unlock the current node
       node.lock.unlock();
     }
     // Traverse
     node = next;      
   }
   // We"re at the final node, so append and then unlock
   try {
     node.rest = new LinkList<E>(value);
     // Let any waiting threads know that this node"s link has changed
     node.linkChanged.signalAll();
   } finally {
     node.lock.unlock();
   }
 }
 public void printUntilInterrupted(String prefix) {
   // Start the pointer at this node
   LinkList<E> node = this;
   node.lock.lock();
   while (true) {
     LinkList<E> next;
     try {
       System.out.println(prefix + ": " + node.value);
       // Wait for the next node if not available
       while (node.rest == null) {
         node.linkChanged.await();
       }
       // Get the next node
       next = node.rest;
       // Lock it - more hand-to-hand locking
       next.lock.lock();
     } catch (InterruptedException e) {
       // reset the interrupt status
       Thread.currentThread().interrupt();
       return;
     } finally {
       node.lock.unlock();
     }
     // Traverse
     node = next;
   }
 }

}


 </source>
   
  
 
  



Condition: signalAll()

   <source lang="java">
 

/* License for Java 1.5 "Tiger": A Developer"s Notebook

    (O"Reilly) example package

Java 1.5 "Tiger": A Developer"s Notebook (O"Reilly) by Brett McLaughlin and David Flanagan. ISBN: 0-596-00738-8 You can use the examples and the source code any way you want, but please include a reference to where it comes from if you use it in your own products or services. Also note that this software is provided by the author "as is", with no expressed or implied warranties. In no event shall the author be liable for any direct or indirect damages arising in any way out of the use of this software.

  • /

import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock;

class LinkList<E> {
 // The value of this node
 E value;
 // The rest of the list
 LinkList<E> rest;

 // A lock for this node
 Lock lock;
 // Signals when the value of this node changes
 Condition valueChanged;
 // Signals when the node this is connected to changes
 Condition linkChanged;
 public LinkList(E value) {
   this.value = value;
   rest = null;
   lock = new ReentrantLock();
   valueChanged = lock.newCondition();
   linkChanged = lock.newCondition();
 }
 public void setValue(E value) {
   lock.lock();
   try {
     this.value = value;
     // Let waiting threads that the value has changed
     valueChanged.signalAll();
   } finally {
     lock.unlock();
   }
 }
 public void executeOnValue(E desiredValue, Runnable task)
   throws InterruptedException {

   lock.lock();
   try {
     // Checks the value against the desired value
     while (!value.equals(desiredValue)) {
       // This will wait until the value changes
       valueChanged.await();
     }
     // When we get here, the value is correct -- Run the task
     task.run();
   } finally {
     lock.unlock();
   }
 }
 public void append(E value) {
   // Start the pointer at this node
   LinkList<E> node = this;
   node.lock.lock();
   while (node.rest != null) {
     LinkList<E> next = node.rest;
     // Here"s the hand-over-hand locking
     try {
       // Lock the next node
       next.lock.lock();
     } finally {
       // unlock the current node
       node.lock.unlock();
     }
     // Traverse
     node = next;      
   }
   // We"re at the final node, so append and then unlock
   try {
     node.rest = new LinkList<E>(value);
     // Let any waiting threads know that this node"s link has changed
     node.linkChanged.signalAll();
   } finally {
     node.lock.unlock();
   }
 }
 public void printUntilInterrupted(String prefix) {
   // Start the pointer at this node
   LinkList<E> node = this;
   node.lock.lock();
   while (true) {
     LinkList<E> next;
     try {
       System.out.println(prefix + ": " + node.value);
       // Wait for the next node if not available
       while (node.rest == null) {
         node.linkChanged.await();
       }
       // Get the next node
       next = node.rest;
       // Lock it - more hand-to-hand locking
       next.lock.lock();
     } catch (InterruptedException e) {
       // reset the interrupt status
       Thread.currentThread().interrupt();
       return;
     } finally {
       node.lock.unlock();
     }
     // Traverse
     node = next;
   }
 }

}


 </source>