diff --git a/classpath/java/util/Collections.java b/classpath/java/util/Collections.java
index d8eda7f619..732df1f706 100644
--- a/classpath/java/util/Collections.java
+++ b/classpath/java/util/Collections.java
@@ -33,8 +33,8 @@ public class Collections {
   }
 
   static class SynchronizedCollection<T> implements Collection<T> {
-    private final Object lock;
-    private final Collection<T> collection;
+    protected final Object lock;
+    protected final Collection<T> collection;
 
     public SynchronizedCollection(Object lock, Collection<T> collection) {
       this.lock = lock;
@@ -73,6 +73,11 @@ public class Collections {
     public SynchronizedSet(Object lock, Set<T> set) {
       super(lock, set);
     }
+
+    public void addAll(Collection<T> c) {
+      synchronized (lock) { ((Set<T>)collection).addAll(c); }
+    }
+
   }
 
   static class SynchronizedIterator<T> implements Iterator<T> {
diff --git a/classpath/java/util/HashMap.java b/classpath/java/util/HashMap.java
index 90795391ef..16337b367a 100644
--- a/classpath/java/util/HashMap.java
+++ b/classpath/java/util/HashMap.java
@@ -286,6 +286,10 @@ public class HashMap<K, V> implements Map<K, V> {
       return HashMap.this.size();
     }
 
+    public void addAll(Collection<Entry<K, V>> c) {
+      throw new UnsupportedOperationException();
+    }
+
     public boolean contains(Entry<K, V> e) {
       return containsKey(e.getKey());
     }
@@ -316,6 +320,10 @@ public class HashMap<K, V> implements Map<K, V> {
       return containsKey(key);
     }
 
+    public void addAll(Collection<K> c) {
+      throw new UnsupportedOperationException();
+    }
+
     public boolean add(K key) {
       return putCell(key, null) != null;
     }
diff --git a/classpath/java/util/Set.java b/classpath/java/util/Set.java
index d01a5ec704..e48d1f1148 100644
--- a/classpath/java/util/Set.java
+++ b/classpath/java/util/Set.java
@@ -1,3 +1,5 @@
 package java.util;
 
-public interface Set<T> extends Collection<T> { }
+public interface Set<T> extends Collection<T> {
+  public void addAll(Collection<T> c);
+}