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diff --git a/vespajlib/src/main/java/com/yahoo/collections/CollectionComparator.java b/vespajlib/src/main/java/com/yahoo/collections/CollectionComparator.java
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+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.collections;
+
+import java.util.Collection;
+import java.util.Iterator;
+
+/**
+ * Utility class which is useful when implementing <code>Comparable</code> and one needs to
+ * compare Collections of Comparables as instance variables.
+ *
+ * @author <a href="mailto:einarmr@yahoo-inc.com">Einar M R Rosenvinge</a>
+ */
+public class CollectionComparator {
+    /**
+     * Compare the arguments. Shorter Collections are always considered
+     * smaller than longer Collections. For Collections of equal lengths, the elements
+     * are compared one-by-one. Whenever two corresponding elements in the
+     * two Collections are non-equal, the method returns. If all elements at
+     * corresponding positions in the two Collections are equal, the Collections
+     * are considered equal.
+     *
+     * @param first a Collection of Comparables to be compared
+     * @param second a Collection of Comparables to be compared
+     * @return 0 if the arguments are equal, -1 if the first argument is smaller, 1 if the second argument is smaller
+     * @throws NullPointerException if any of the arguments are null
+     */
+    @SuppressWarnings({"rawtypes", "unchecked"})
+    public static int compare(Collection<? extends Comparable> first, Collection<? extends Comparable> second) {
+        if (first.size() < second.size()) {
+            return -1;
+        }
+        if (first.size() > second.size()) {
+            return 1;
+        }
+
+        //sizes are equal, compare contents
+        Iterator<? extends Comparable> firstIt = first.iterator();
+        Iterator<? extends Comparable> secondIt = second.iterator();
+
+        while (firstIt.hasNext()) {
+            // FIXME: unchecked casting
+            Comparable itemFirst = firstIt.next();
+            Comparable itemSecond = secondIt.next();
+            int comp = itemFirst.compareTo(itemSecond);
+            if (comp != 0) {
+                return comp;
+            }
+            //values are equal, continue...
+        }
+
+        //we haven't returned yet; contents must be equal:
+        return 0;
+    }
+}