Scala example source code file (MailBox.scala)

This example Scala source code file (MailBox.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

any, any, boolean, linkedlist, linkedlist, long, mailbox, partialfunction, partialfunction, receiver, receiver, timeout, unit

The Scala MailBox.scala source code

package test;

import scala.concurrent._;

class MailBox {
  private class LinkedList[a] {
    var elem: a = _;
    var next: LinkedList[a] = null;
  }

  private def insert[a](l: LinkedList[a], x: a): LinkedList[a] = {
    l.next = new LinkedList[a];
    l.next.elem = x;
    l.next.next = l.next;
    l
  }

  private abstract class Receiver {
    def isDefined(msg: Any): Boolean;
    var msg: Any = null;
  }

  private val sent = new LinkedList[Any];
  private var lastSent = sent;
  private val receivers = new LinkedList[Receiver];
  private var lastReceiver = receivers; 

  def send(msg: Any): Unit = synchronized {
    var r = receivers;
    var r1 = r.next;
    while (r1 != null && !r1.elem.isDefined(msg)) {
      r = r1; r1 = r1.next;
    }
    if (r1 != null) {
      r.next = r1.next; r1.elem.msg = msg; r1.elem.notify();
    } else {
      lastSent = insert(lastSent, msg);
    }
  }

  def receive[a](f: PartialFunction[Any, a]): a = {
    val msg: Any = synchronized {
      var s = sent;
      var s1 = s.next;
      while (s1 != null && !f.isDefinedAt(s1.elem)) {
        s = s1; s1 = s1.next
      }
      if (s1 != null) {
        s.next = s1.next; s1.elem
      } else {
	val r = insert(lastReceiver, new Receiver {
          def isDefined(msg: Any) = f.isDefinedAt(msg);
        });
	lastReceiver = r;
        r.elem.wait();
        r.elem.msg
      }
    }
    f(msg)
  }
  
  def receiveWithin[a](msec: Long)(f: PartialFunction[Any, a]): a = {
    val msg: Any = synchronized {
      var s = sent;
      var s1 = s.next;
      while (s1 != null && !f.isDefinedAt(s1.elem)) {
        s = s1; s1 = s1.next ;
      }
      if (s1 != null) {
        s.next = s1.next; s1.elem
      } else {
        val r = insert(lastReceiver, new Receiver {
            def isDefined(msg: Any) = f.isDefinedAt(msg);
        });
        lastReceiver = r;
        r.elem.wait(msec);
        if (r.elem.msg == null) r.elem.msg = TIMEOUT;
        r.elem.msg
      }
    }
    f(msg)
  }
}