--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/EDU/oswego/cs/dl/util/concurrent/SynchronizedBoolean.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,175 @@
+/*
+  File: SynchronizedBoolean.java
+
+  Originally written by Doug Lea and released into the public domain.
+  This may be used for any purposes whatsoever without acknowledgment.
+  Thanks for the assistance and support of Sun Microsystems Labs,
+  and everyone contributing, testing, and using this code.
+
+  History:
+  Date       Who                What
+  19Jun1998  dl               Create public version
+*/
+
+package EDU.oswego.cs.dl.util.concurrent;
+
+/**
+ * A class useful for offloading synch for boolean instance variables.
+ *
+ * <p>[<a href="http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html"> Introduction to this package. </a>]
+ **/
+
+public class SynchronizedBoolean  extends SynchronizedVariable implements Comparable, Cloneable {
+  protected boolean value_;
+
+  /** 
+   * Make a new SynchronizedBoolean with the given initial value,
+   * and using its own internal lock.
+   **/
+  public SynchronizedBoolean(boolean initialValue) { 
+    super(); 
+    value_ = initialValue; 
+  }
+
+  /** 
+   * Make a new SynchronizedBoolean with the given initial value,
+   * and using the supplied lock.
+   **/
+  public SynchronizedBoolean(boolean initialValue, Object lock) { 
+    super(lock); 
+    value_ = initialValue; 
+  }
+
+  /** 
+   * Return the current value 
+   **/
+  public final boolean get() { synchronized(lock_) { return value_; } }
+
+  /** 
+   * Set to newValue.
+   * @return the old value 
+   **/
+
+  public boolean set(boolean newValue) { 
+    synchronized (lock_) {
+      boolean old = value_;
+      value_ = newValue; 
+      return old;
+    }
+  }
+
+  /**
+   * Set value to newValue only if it is currently assumedValue.
+   * @return true if successful
+   **/
+  public boolean commit(boolean assumedValue, boolean newValue) {
+    synchronized(lock_) {
+      boolean success = (assumedValue == value_);
+      if (success) value_ = newValue;
+      return success;
+    }
+  }
+
+  /** 
+   * Atomically swap values with another SynchronizedBoolean.
+   * Uses identityHashCode to avoid deadlock when
+   * two SynchronizedBooleans attempt to simultaneously swap with each other.
+   * (Note: Ordering via identyHashCode is not strictly guaranteed
+   * by the language specification to return unique, orderable
+   * values, but in practice JVMs rely on them being unique.)
+   * @return the new value 
+   **/
+
+  public boolean swap(SynchronizedBoolean other) {
+    if (other == this) return get();
+    SynchronizedBoolean fst = this;
+    SynchronizedBoolean snd = other;
+    if (System.identityHashCode(fst) > System.identityHashCode(snd)) {
+      fst = other;
+      snd = this;
+    }
+    synchronized(fst.lock_) {
+      synchronized(snd.lock_) {
+        fst.set(snd.set(fst.get()));
+        return get();
+      }
+    }
+  }
+
+  /** 
+   * Set the value to its complement
+   * @return the new value 
+   **/
+  public  boolean complement() { 
+    synchronized (lock_) {
+      value_ = !value_;
+      return value_;
+    }
+  }
+
+  /** 
+   * Set value to value &amp; b.
+   * @return the new value 
+   **/
+  public  boolean and(boolean b) { 
+    synchronized (lock_) {
+      value_ = value_ & b;
+      return value_;
+    }
+  }
+
+  /** 
+   * Set value to value | b.
+   * @return the new value 
+   **/
+  public  boolean or(boolean b) { 
+    synchronized (lock_) {
+      value_ = value_ | b;
+      return value_;
+    }
+  }
+
+
+  /** 
+   * Set value to value ^ b.
+   * @return the new value 
+   **/
+  public  boolean xor(boolean b) { 
+    synchronized (lock_) {
+      value_ = value_ ^ b;
+      return value_;
+    }
+  }
+
+
+  public int compareTo(boolean other) {
+    boolean val = get();
+    return  (val == other)? 0 : (val)? 1 : -1;
+  }
+
+  public int compareTo(SynchronizedBoolean other) {
+    return compareTo(other.get());
+  }
+
+  public int compareTo(Object other) {
+    return compareTo((SynchronizedBoolean)other);
+  }
+  
+
+  public boolean equals(Object other) {
+    if (other != null &&
+        other instanceof SynchronizedBoolean)
+      return get() == ((SynchronizedBoolean)other).get();
+    else
+      return false;
+  }
+
+  public int hashCode() { 
+    boolean b = get(); 
+    return (b)? 3412688 :  8319343; // entirely arbitrary
+  }
+
+  public String toString() { return String.valueOf(get()); }
+
+}
+