added Java compat API for defining up ActiveObjects

kernel/src/main/scala/ErrRef.scala

@@ -0,0 +1,50 @@
+/**
+ * Copyright (C) 2009 Scalable Solutions.
+ */
+
+package com.scalablesolutions.akka.kernel
+
+/**
+ * Reference that can hold either a typed value or an exception.
+ *
+ * Usage:
+ * <pre>
+ * scala> ErrRef(1)
+ * res0: ErrRef[Int] = ErrRef@a96606
+ *  
+ * scala> res0()
+ * res1: Int = 1
+ *
+ * scala> res0() = 3
+ *
+ * scala> res0()
+ * res3: Int = 3
+ * 
+ * scala> res0() = { println("Hello world"); 3}
+ * Hello world
+ *
+ * scala> res0()
+ * res5: Int = 3
+ *  
+ * scala> res0() = error("Lets see what happens here...")
+ *
+ * scala> res0()
+ * java.lang.RuntimeException: Lets see what happens here...
+ * 	at ErrRef.apply(RefExcept.scala:11)
+ * 	at .<init>(<console>:6)
+ * 	at .<clinit>(<console>)
+ * 	at Re...
+ * </pre>
+ */
+class ErrRef[S](s: S){
+  private[this] var contents: Either[Throwable, S] = Right(s)
+  def update(value: => S) = contents = try { Right(value) } catch { case (e : Throwable) => Left(e) }
+  def apply() = contents match {
+    case Right(s) => s
+    case Left(e) => throw e.fillInStackTrace
+  }
+  override def toString(): String = "ErrRef[" + contents + "]"
+}
+object ErrRef {
+  def apply[S](s: S) = new ErrRef(s)
+}