Some small classpath tweaks to be compatible with openJDK's api

classpath/java/util/Collections.java

@@ -38,7 +38,11 @@ public class Collections {
   public static void sort(List list) {
     sort(list, new Comparator() {
         public int compare(Object a, Object b) {
-          return ((Comparable) a).compareTo(b);
+          if (a instanceof Comparable) {
+            return ((Comparable) a).compareTo(b);
+          } else {
+            return a.hashCode() - b.hashCode();
+          }
         }
       });
   }

classpath/java/util/concurrent/ConcurrentHashMap.java

@@ -49,6 +49,14 @@ public class ConcurrentHashMap<K,V>
     this();
   }
 
+  public ConcurrentHashMap(int initialCapacity,  float loadFactor) {
+    this();
+  }
+
+  public ConcurrentHashMap(int initialCapacity,  float loadFactor, int concurrencyLevel) {
+    this();
+  }
+
   public boolean isEmpty() {
     return content.size == 0;
   }

classpath/java/util/concurrent/Delayed.java

@@ -10,6 +10,6 @@
 
 package java.util.concurrent;
 
-public interface Delayed {
+public interface Delayed extends Comparable<Delayed> {
   public long getDelay(TimeUnit unit);
 }

classpath/java/util/concurrent/ExecutorService.java

@@ -14,6 +14,8 @@ import java.util.Collection;
 
 public interface ExecutorService extends Executor {
     public void shutdown();
+    
+    public List<Runnable> shutdownNow();
 
     public boolean isShutdown();
 

classpath/java/util/concurrent/Executors.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;
+
+public class Executors {
+  public static <T> Callable<T> callable(final Runnable task, final T result) {
+    return new Callable<T>() {
+      @Override
+      public T call() throws Exception {
+        task.run();
+        
+        return result;
+      }
+    };
+  }
+}