diff --git a/classpath/java/lang/Thread.java b/classpath/java/lang/Thread.java
index 095691d342..5d99c2f092 100644
--- a/classpath/java/lang/Thread.java
+++ b/classpath/java/lang/Thread.java
@@ -14,6 +14,9 @@ import java.util.Map;
 import java.util.WeakHashMap;
 
 public class Thread implements Runnable {
+  // set and accessed from within LockSupport
+  protected volatile Object parkBlocker;
+  
   private long peer;
   private volatile boolean interrupted;
   private volatile boolean unparked;
diff --git a/classpath/java/util/Deque.java b/classpath/java/util/Deque.java
new file mode 100644
index 0000000000..2739965411
--- /dev/null
+++ b/classpath/java/util/Deque.java
@@ -0,0 +1,31 @@
+/* Copyright (c) 2008-2014, Avian Contributors
+
+   Permission to use, copy, modify, and/or distribute this software
+   for any purpose with or without fee is hereby granted, provided
+   that the above copyright notice and this permission notice appear
+   in all copies.
+
+   There is NO WARRANTY for this software.  See license.txt for
+   details. */
+
+package java.util;
+
+public interface Deque<T> extends Queue<T> {
+  public boolean offerFirst(T e);
+  public void push(T e);
+  public void addFirst(T element);
+  public boolean offerLast(T e);
+  public void addLast(T element);
+  public T peekFirst();
+  public T getFirst();
+  public T peekLast();
+  public T getLast();
+  public T pollFirst();
+  public T removeFirst();
+  public T pop();
+  public T pollLast();
+  public T removeLast();
+  public Iterator<T> descendingIterator();
+  public boolean removeLastOccurrence(Object o);
+  public boolean removeFirstOccurrence(Object o);
+}
diff --git a/classpath/java/util/LinkedList.java b/classpath/java/util/LinkedList.java
index e161a7714e..d42c6961b2 100644
--- a/classpath/java/util/LinkedList.java
+++ b/classpath/java/util/LinkedList.java
@@ -10,7 +10,7 @@
 
 package java.util;
 
-public class LinkedList<T> extends AbstractSequentialList<T> {
+public class LinkedList<T> extends AbstractSequentialList<T> implements Deque<T> {
   private Cell<T> front;
   private Cell<T> rear;
   private int size;
@@ -85,14 +85,17 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
     }
   }
 
+  @Override
   public int size() {
     return size;
   }
 
+  @Override
   public boolean contains(Object element) {
     return find(element) != null;
   }
 
+  @Override
   public int indexOf(Object element) {
     int i = 0;
     for (Cell<T> c = front; c != null; c = c.next) {
@@ -104,6 +107,7 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
     return -1;
   }
 
+  @Override
   public int lastIndexOf(Object element) {
     int i = size;
     for (Cell<T> c = rear; c != null; c = c.prev) {
@@ -115,16 +119,24 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
     return -1;
   }
 
+  @Override
+  public boolean offer(T element) {
+    return add(element);
+  }
+
+  @Override
   public boolean add(T element) {
     addLast(element);
     return true;
   }
 
+  @Override
   public boolean addAll(Collection<? extends T> collection) {
     for (T t: collection) add(t);
     return true;
   }
 
+  @Override
   public void add(int index, T element) {
     if (index == 0) {
       addFirst(element);
@@ -135,10 +147,31 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
     }
   }
 
+  @Override
+  public boolean offerFirst(T e) {
+    addFirst(e);
+    
+    return true;
+  }
+
+  @Override
+  public void push(T e) {
+    addFirst(e);
+  }
+
+  @Override
   public void addFirst(T element) {
     addFirst(new Cell(element, null, null));
   }
 
+  @Override
+  public boolean offerLast(T e) {
+    addLast(e);
+    
+    return true;
+  }
+
+  @Override
   public void addLast(T element) {
     addLast(new Cell(element, null, null));
   }
@@ -147,6 +180,7 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
     return find(index).value;
   }
 
+  @Override
   public T set(int index, T value) {
     Cell<T> c = find(index);
     T old = c.value;
@@ -154,6 +188,21 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
     return old;
   }
 
+  @Override
+  public T peek() {
+    return peekFirst();
+  }
+
+  @Override
+  public T peekFirst() {
+    if (front != null) {
+      return front.value;
+    } else {
+      return null;
+    }
+  }
+
+  @Override
   public T getFirst() {
     if (front != null) {
       return front.value;
@@ -161,7 +210,17 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
       throw new NoSuchElementException();
     }
   }
+  
+  @Override
+  public T peekLast() {
+    if (rear != null) {
+      return rear.value;
+    } else {
+      return null;
+    }
+  }
 
+  @Override
   public T getLast() {
     if (rear != null) {
       return rear.value;
@@ -170,27 +229,57 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
     }
   }
 
+  @Override
   public T remove(int index) {
     Cell<T> c = find(index);
     remove(c);
     return c.value;
   }
 
+  @Override
   public boolean isEmpty() {
     return size() == 0;
   }
 
-  public T removeFirst() {
+  @Override
+  public T poll() {
+    return pollFirst();
+  }
+
+  @Override
+  public T pollFirst() {
     if (front != null) {
       T v = front.value;
       remove(front);
       return v;
     } else {
-      throw new NoSuchElementException();
+      return null;
     }
   }
 
-  public T removeLast() {
+  @Override
+  public T removeFirst() {
+    T result = pollFirst();
+    
+    if (result == null) {
+      throw new NoSuchElementException();
+    } else {
+      return result;
+    }
+  }
+
+  @Override
+  public T pop() {
+    return removeFirst();
+  }
+
+  @Override
+  public T remove() {
+    return removeFirst();
+  }
+
+  @Override
+  public T pollLast() {
     if (rear != null) {
       T v = rear.value;
       remove(rear);
@@ -200,6 +289,18 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
     }
   }
 
+  @Override
+  public T removeLast() {
+    T result = pollLast();
+    
+    if (result == null) {
+      throw new NoSuchElementException();
+    } else {
+      return result;
+    }
+  }
+
+  @Override
   public boolean remove(Object element) {
     Cell<T> c = find(element);
     if (c == null) {
@@ -210,15 +311,23 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
     }
   }
 
+  @Override
   public void clear() {
     front = rear = null;
     size = 0;
   }
 
+  @Override
   public Iterator<T> iterator() {
     return listIterator();
   }
 
+  @Override
+  public ListIterator<T> listIterator() {
+    return listIterator(0);
+  }
+
+  @Override
   public ListIterator<T> listIterator(int index) {
     MyIterator it = new MyIterator();
     for (int i = 0; i < index; ++i) {
@@ -227,14 +336,67 @@ public class LinkedList<T> extends AbstractSequentialList<T> {
     return it;
   }
 
-  public ListIterator<T> listIterator() {
-    return listIterator(0);
+  @Override
+  public Iterator<T> descendingIterator() {
+    final ListIterator<T> li = listIterator(size());
+    
+    return new Iterator<T>() {
+      @Override
+      public T next() {
+        return li.previous();
+      }
+
+      @Override
+      public boolean hasNext() {
+        return li.hasPrevious();
+      }
+
+      @Override
+      public void remove() {
+        li.remove();
+      }
+    };
   }
 
+  @Override
   public String toString() {
     return Collections.toString(this);
   }
 
+  @Override
+  public T element() {
+    T result = peek();
+    if (result == null) {
+      throw new NoSuchElementException();
+    } else {
+      return result;
+    }
+  }
+
+  @Override
+  public boolean removeFirstOccurrence(Object o) {
+    int index = indexOf(o);
+    if (index > 0) {
+      remove(index);
+      
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  @Override
+  public boolean removeLastOccurrence(Object o) {
+    int lastIndex = lastIndexOf(o);
+    if (lastIndex > 0) {
+      remove(lastIndex);
+      
+      return true;
+    } else {
+      return false;
+    }
+  }
+  
   private static class Cell<T> {
     public T value;
     public Cell<T> prev;
diff --git a/classpath/java/util/concurrent/ConcurrentLinkedQueue.java b/classpath/java/util/concurrent/ConcurrentLinkedQueue.java
index 93105317f2..357f8a7ded 100644
--- a/classpath/java/util/concurrent/ConcurrentLinkedQueue.java
+++ b/classpath/java/util/concurrent/ConcurrentLinkedQueue.java
@@ -1,8 +1,13 @@
 package java.util.concurrent;
 
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Queue;
+
 import avian.Atomic;
 
-public class ConcurrentLinkedQueue<T> {
+public class ConcurrentLinkedQueue<T> implements Queue<T> {
   private static final long QueueHead;
   private static final long QueueTail;
   private static final long NodeNext;
@@ -25,11 +30,20 @@ public class ConcurrentLinkedQueue<T> {
   private volatile Node<T> head = new Node<T>(null, null);
   private volatile Node<T> tail = head;
 
+  @Override
   public void clear() {
-    // todo: can we safely make this O(1)?
+    // TODO - can we safely make this O(1)?
     while (poll() != null) { }
   }
 
+  @Override
+  public boolean offer(T element) {
+    add(element);
+    
+    return true;
+  }
+
+  @Override
   public boolean add(T value) {
     Node<T> n = new Node<T>(value, null);
     while (true) {
@@ -48,14 +62,36 @@ public class ConcurrentLinkedQueue<T> {
     return true;
   }
 
+  @Override
   public T peek() {
     return poll(false);
   }
 
+  @Override
+  public T element() {
+    T result = peek();
+    if (result == null) {
+      throw new NoSuchElementException();
+    } else {
+      return result;
+    }
+  }
+
+  @Override
   public T poll() {
     return poll(true);
   }
 
+  @Override
+  public T remove() {
+    T result = poll();
+    if (result == null) {
+      throw new NoSuchElementException();
+    } else {
+      return result;
+    }
+  }
+
   private T poll(boolean remove) {
     while (true) {
       Node<T> h = head;
@@ -90,4 +126,63 @@ public class ConcurrentLinkedQueue<T> {
       this.next = next;
     }
   }
+
+  @Override
+  public int size() {
+    // TODO - implement
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public boolean isEmpty() {
+    return size() == 0;
+  }
+
+  @Override
+  public boolean contains(Object element) {
+    // TODO - implement
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public boolean containsAll(Collection<?> c) {
+    // TODO - implement
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public boolean addAll(Collection<? extends T> collection) {
+    // TODO - implement
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public boolean remove(Object element) {
+    // TODO - implement
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public boolean removeAll(Collection<?> c) {
+    // TODO - implement
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public Object[] toArray() {
+    // TODO - implement
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public <S> S[] toArray(S[] array) {
+    // TODO - implement
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public Iterator<T> iterator() {
+    // TODO - implement
+    throw new UnsupportedOperationException();
+  }
 }
diff --git a/classpath/java/util/concurrent/locks/Condition.java b/classpath/java/util/concurrent/locks/Condition.java
new file mode 100644
index 0000000000..7a021eb289
--- /dev/null
+++ b/classpath/java/util/concurrent/locks/Condition.java
@@ -0,0 +1,24 @@
+/* Copyright (c) 2008-2014, Avian Contributors
+
+   Permission to use, copy, modify, and/or distribute this software
+   for any purpose with or without fee is hereby granted, provided
+   that the above copyright notice and this permission notice appear
+   in all copies.
+
+   There is NO WARRANTY for this software.  See license.txt for
+   details. */
+
+package java.util.concurrent.locks;
+
+import java.util.Date;
+import java.util.concurrent.TimeUnit;
+
+public interface Condition {
+  public void await();
+  public boolean await(long time, TimeUnit unit);
+  public long awaitNanos(long nanosTimeout);
+  public void awaitUninterruptibly();
+  public boolean awaitUntil(Date deadline);
+  public void signal();
+  public void signalAll();
+}
diff --git a/classpath/java/util/concurrent/locks/Lock.java b/classpath/java/util/concurrent/locks/Lock.java
new file mode 100644
index 0000000000..f2fb9b0792
--- /dev/null
+++ b/classpath/java/util/concurrent/locks/Lock.java
@@ -0,0 +1,22 @@
+/* Copyright (c) 2008-2014, Avian Contributors
+
+   Permission to use, copy, modify, and/or distribute this software
+   for any purpose with or without fee is hereby granted, provided
+   that the above copyright notice and this permission notice appear
+   in all copies.
+
+   There is NO WARRANTY for this software.  See license.txt for
+   details. */
+
+package java.util.concurrent.locks;
+
+import java.util.concurrent.TimeUnit;
+
+public interface Lock {
+  public void lock();
+  public void lockInterruptibly() throws InterruptedException;
+  public Condition newCondition();
+  public boolean tryLock();
+  public boolean tryLock(long time, TimeUnit unit) throws InterruptedException;
+  public void unlock();
+}
diff --git a/classpath/java/util/concurrent/locks/LockSupport.java b/classpath/java/util/concurrent/locks/LockSupport.java
new file mode 100644
index 0000000000..1f547c465d
--- /dev/null
+++ b/classpath/java/util/concurrent/locks/LockSupport.java
@@ -0,0 +1,89 @@
+/* Copyright (c) 2008-2014, Avian Contributors
+
+   Permission to use, copy, modify, and/or distribute this software
+   for any purpose with or without fee is hereby granted, provided
+   that the above copyright notice and this permission notice appear
+   in all copies.
+
+   There is NO WARRANTY for this software.  See license.txt for
+   details. */
+
+package java.util.concurrent.locks;
+
+import sun.misc.Unsafe;
+
+public class LockSupport {
+  private LockSupport() {
+    // can't construct
+  }
+  
+  private static final Unsafe unsafe;
+  private static final long parkBlockerOffset;
+  
+  static {
+    unsafe = Unsafe.getUnsafe();
+    try {
+      parkBlockerOffset = unsafe.objectFieldOffset(java.lang.Thread.class.getDeclaredField("parkBlocker"));
+    } catch (Exception ex) { 
+      throw new Error(ex);
+    }
+  }
+  
+  private static void setBlocker(Thread t, Object arg) {
+    unsafe.putObject(t, parkBlockerOffset, arg);
+  }
+  
+  public static void unpark(Thread thread) {
+    if (thread != null) {
+      unsafe.unpark(thread);
+    }
+  }
+  
+  public static void park(Object blocker) {
+    doParkNanos(blocker, 0L);
+  }
+  
+  public static void parkNanos(Object blocker, long nanos) {
+    if (nanos <= 0) {
+      return;
+    }
+    
+    doParkNanos(blocker, nanos);
+  }
+  
+  private static void doParkNanos(Object blocker, long nanos) {
+    Thread t = Thread.currentThread();
+    setBlocker(t, blocker);
+    unsafe.park(false, nanos);
+    setBlocker(t, null);
+  }
+  
+  public static void parkUntil(Object blocker, long deadline) {
+    Thread t = Thread.currentThread();
+    setBlocker(t, blocker);
+    unsafe.park(true, deadline);
+    setBlocker(t, null);
+  }
+  
+  public static Object getBlocker(Thread t) {
+    if (t == null) {
+      throw new NullPointerException();
+    }
+    
+    return unsafe.getObjectVolatile(t, parkBlockerOffset);
+  }
+  
+  public static void park() {
+    unsafe.park(false, 0L);
+  }
+  
+  public static void parkNanos(long nanos) {
+    if (nanos > 0) {
+      unsafe.park(false, nanos);
+    }
+  }
+  
+  public static void parkUntil(long deadline) {
+    unsafe.park(true, deadline);
+  }
+}
diff --git a/classpath/java/util/concurrent/locks/ReadWriteLock.java b/classpath/java/util/concurrent/locks/ReadWriteLock.java
new file mode 100644
index 0000000000..a4804e5fa4
--- /dev/null
+++ b/classpath/java/util/concurrent/locks/ReadWriteLock.java
@@ -0,0 +1,16 @@
+/* Copyright (c) 2008-2014, Avian Contributors
+
+   Permission to use, copy, modify, and/or distribute this software
+   for any purpose with or without fee is hereby granted, provided
+   that the above copyright notice and this permission notice appear
+   in all copies.
+
+   There is NO WARRANTY for this software.  See license.txt for
+   details. */
+
+package java.util.concurrent.locks;
+
+public interface ReadWriteLock {
+  public Lock readLock();
+  public Lock writeLock();
+}
diff --git a/src/classpath-avian.cpp b/src/classpath-avian.cpp
index dbbf821828..e49d4fa0c1 100644
--- a/src/classpath-avian.cpp
+++ b/src/classpath-avian.cpp
@@ -52,7 +52,7 @@ class MyClasspath : public Classpath {
     const unsigned NormalPriority = 5;
 
     return vm::makeThread
-      (t, 0, 0, 0, 0, NewState, NormalPriority, 0, 0, 0,
+      (t, 0, 0, 0, 0, 0, NewState, NormalPriority, 0, 0, 0,
        root(t, Machine::AppLoader), 0, 0, group, 0);
   }