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diff --git a/src/main/java/com/google/escapevelocity/ImmutableList.java b/src/main/java/com/google/escapevelocity/ImmutableList.java
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+++ b/src/main/java/com/google/escapevelocity/ImmutableList.java
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+/*
+ * Copyright (C) 2017 Google, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.escapevelocity;
+
+import java.util.AbstractList;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * An immutable list.
+ *
+ * @author emcmanus@google.com (Éamonn McManus)
+ */
+class ImmutableList<E> extends AbstractList<E> {
+  private static final ImmutableList<?> EMPTY = new ImmutableList<>(new Object[0]);
+
+  private final E[] elements;
+
+  private ImmutableList(E[] elements) {
+    this.elements = elements;
+  }
+
+  @Override
+  public Iterator<E> iterator() {
+    return Arrays.asList(elements).iterator();
+  }
+
+  @Override
+  public E get(int index) {
+    if (index < 0 || index >= elements.length) {
+      throw new IndexOutOfBoundsException(String.valueOf(index));
+    }
+    return elements[index];
+  }
+
+  @Override
+  public int size() {
+    return elements.length;
+  }
+
+  static <E> ImmutableList<E> of() {
+    @SuppressWarnings("unchecked")
+    ImmutableList<E> empty = (ImmutableList<E>) EMPTY;
+    return empty;
+  }
+
+  @SafeVarargs
+  static <E> ImmutableList<E> of(E... elements) {
+    return new ImmutableList<>(elements.clone());
+  }
+
+  static <E> ImmutableList<E> copyOf(List<E> list) {
+    @SuppressWarnings("unchecked")
+    E[] elements = (E[]) new Object[list.size()];
+    list.toArray(elements);
+    return new ImmutableList<>(elements);
+  }
+
+  static <E> Builder<E> builder() {
+    return new Builder<E>();
+  }
+
+  static class Builder<E> {
+    private final List<E> list = new ArrayList<>();
+
+    void add(E element) {
+      list.add(element);
+    }
+
+    ImmutableList<E> build() {
+      if (list.isEmpty()) {
+        return ImmutableList.of();
+      }
+      @SuppressWarnings("unchecked")
+      E[] elements = (E[]) new Object[list.size()];
+      list.toArray(elements);
+      return new ImmutableList<>(elements);
+    }
+  }
+}