--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main/java/fj/data/fingertrees/Empty.java	Fri Mar 20 21:04:03 2015 +0900
@@ -0,0 +1,69 @@
+package fj.data.fingertrees;
+
+import fj.F;
+import fj.P2;
+import static fj.Bottom.error;
+
+/**
+ * The empty tree.
+ */
+public final class Empty<V, A> extends FingerTree<V, A> {
+  Empty(final Measured<V, A> m) {
+    super(m);
+  }
+
+  @Override public FingerTree<V, A> cons(final A a) {
+    return new Single<V, A>(measured(), a);
+  }
+
+  @Override public FingerTree<V, A> snoc(final A a) {
+    return cons(a);
+  }
+
+  @Override public FingerTree<V, A> append(final FingerTree<V, A> t) {
+    return t;
+  }
+
+  @Override public P2<Integer, A> lookup(final F<V, Integer> o, final int i) {
+    throw error("Lookup of empty tree.");
+  }
+
+  @Override public <B> B foldRight(final F<A, F<B, B>> aff, final B z) {
+    return z;
+  }
+
+  public A reduceRight(final F<A, F<A, A>> aff) {
+    throw error("Reduction of empty tree");
+  }
+
+  @Override public <B> B foldLeft(final F<B, F<A, B>> bff, final B z) {
+    return z;
+  }
+
+  @Override public A reduceLeft(final F<A, F<A, A>> aff) {
+    throw error("Reduction of empty tree");
+  }
+
+  @Override public <B> FingerTree<V, B> map(final F<A, B> abf, final Measured<V, B> m) {
+    return new Empty<V, B>(m);
+  }
+
+  /**
+   * Returns zero.
+   *
+   * @return Zero.
+   */
+  public V measure() {
+    return measured().zero();
+  }
+
+  /**
+   * Pattern matching on the structure of this tree. Matches the empty tree.
+   */
+  @Override public <B> B match(
+      final F<Empty<V, A>, B> empty, final F<Single<V, A>, B> single, final F<Deep<V, A>, B> deep) {
+    return empty.f(this);
+  }
+
+
+}