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diff --git a/vespajlib/src/main/java/com/yahoo/yolean/concurrent/ThreadRobustList.java b/vespajlib/src/main/java/com/yahoo/yolean/concurrent/ThreadRobustList.java
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+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.yolean.concurrent;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * <p>This class implements a thread-safe, lock-free list of Objects that supports multiple readers and a single writer.
+ * Because there are no locks or other memory barriers involved, there exists no <i>happens-before</i> relationship
+ * among calls to either methods of the <code>ThreadRobustList</code>. This means that there are no guarantees as to when
+ * (or even if) an item {@link #add(Object)}ed becomes visible through {@link #iterator()}. If visibility is required,
+ * either use explicit synchronization between reader and writer thread, or move to a different concurrent collection
+ * (e.g. <code>CopyOnWriteArrayList</code>).</p>
+ * <p>Because it is lock-free, the <code>ThreadRobustList</code> has minimal overhead to both reading and writing. The
+ * iterator offered by this class always observes the list in a consistent state, and it never throws a
+ * <code>ConcurrentModificationException</code>.</p>
+ * <p>The <code>ThreadRobustList</code> does not permit adding <code>null</code> items.</p>
+ * <p>The usage of <code>ThreadRobustList</code> has no memory consistency effects. </p>
+ *
+ * @author Steinar Knutsen
+ * @author bratseth
+ * @since 5.1.15
+ */
+public class ThreadRobustList<T> implements Iterable<T> {
+
+    private Object[] items;
+    private int next = 0;
+
+    /**
+     * <p>Constructs a new instance of this class with an initial capacity of <code>10</code>.</p>
+     */
+    public ThreadRobustList() {
+        this(10);
+    }
+
+    /**
+     * <p>Constructs a new instance of this class with a given initial capacity.</p>
+     *
+     * @param initialCapacity the initial capacity of this list
+     */
+    public ThreadRobustList(int initialCapacity) {
+        items = new Object[initialCapacity];
+    }
+
+    /**
+     * <p>Returns whether or not this list is empty.</p>
+     *
+     * @return <code>true</code> if this list has zero items
+     */
+    public boolean isEmpty() {
+        return next == 0;
+    }
+
+    /**
+     * <p>Adds an item to this list. As opposed to <code>CopyOnWriteArrayList</code>, items added to this list may become
+     * visible to iterators created <em>before</em> a call to this method.</p>
+     *
+     * @param item the item to add
+     * @throws NullPointerException if <code>item</code> is <code>null</code>
+     */
+    public void add(T item) {
+        if (item == null) {
+            throw new NullPointerException();
+        }
+        Object[] workItems = items;
+        if (next >= items.length) {
+            workItems = Arrays.copyOf(workItems, 20 + items.length * 2);
+            workItems[next++] = item;
+            items = workItems;
+        } else {
+            workItems[next++] = item;
+        }
+    }
+
+    /**
+     * <p>Returns an iterator over the items in this list. As opposed to <code>CopyOnWriteArrayList</code>, this iterator
+     * may see items added to the <code>ThreadRobustList</code> even if they occur <em>after</em> a call to this method.</p>
+     * <p>The returned iterator does not support <code>remove()</code>.</p>
+     *
+     * @return an iterator over this list
+     */
+    @Override
+    public Iterator<T> iterator() {
+        return new ThreadRobustIterator<>(items);
+    }
+
+    private static class ThreadRobustIterator<T> implements Iterator<T> {
+
+        final Object[] items;
+        int nextIndex = 0;
+
+        ThreadRobustIterator(Object[] items) {
+            this.items = items;
+        }
+
+        @Override
+        public void remove() {
+            throw new UnsupportedOperationException();
+        }
+
+        @SuppressWarnings("unchecked")
+        @Override
+        public T next() {
+            if (!hasNext()) {
+                throw new NoSuchElementException();
+            }
+            return (T)items[nextIndex++];
+        }
+
+        @Override
+        public boolean hasNext() {
+            if (nextIndex >= items.length) {
+                return false;
+            }
+            if (items[nextIndex] == null) {
+                return false;
+            }
+            return true;
+        }
+    }
+}