--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/EDU/oswego/cs/dl/util/concurrent/Barrier.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,61 @@
+
+/*
+  File: Barrier.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
+  11Jun1998  dl               Create public version
+*/
+
+package EDU.oswego.cs.dl.util.concurrent;
+
+/**
+ * Barriers serve
+ * as synchronization points for groups of threads that
+ * must occasionally wait for each other. 
+ * Barriers may support any of several methods that
+ * accomplish this synchronization. This interface
+ * merely expresses their minimal commonalities:
+ * <ul>
+ *   <li> Every barrier is defined for a given number
+ *     of <code>parties</code> -- the number of threads
+ *     that must meet at the barrier point. (In all current
+ *     implementations, this
+ *     value is fixed upon construction of the Barrier.)
+ *   <li> A barrier can become <code>broken</code> if
+ *     one or more threads leave a barrier point prematurely,
+ *     generally due to interruption or timeout. Corresponding
+ *     synchronization methods in barriers fail, throwing
+ *     BrokenBarrierException for other threads
+ *     when barriers are in broken states.
+ * </ul>
+ * <p>[<a href="http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html"> Introduction to this package. </a>]
+
+ **/
+public interface Barrier {
+
+
+  /** 
+   * Return the number of parties that must meet per barrier
+   * point. The number of parties is always at least 1.
+   **/
+
+  public int parties();
+
+  /**
+   * Returns true if the barrier has been compromised
+   * by threads leaving the barrier before a synchronization
+   * point (normally due to interruption or timeout). 
+   * Barrier methods in implementation classes throw
+   * throw BrokenBarrierException upon detection of breakage.
+   * Implementations may also support some means
+   * to clear this status.
+   **/
+
+  public boolean broken();
+}