classlib: inheritDeque from SequencedCollection, fix ArrayDeque (#765)

Second part of JEP-431

classlib/src/main/java/org/teavm/classlib/java/util/TArrayDeque.java

@@ -16,9 +16,10 @@
 package org.teavm.classlib.java.util;
 
 import java.util.Arrays;
-import org.teavm.classlib.java.lang.*;
+import org.teavm.classlib.java.io.TSerializable;
+import org.teavm.classlib.java.lang.TCloneable;
 
-public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E> {
+public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>, TCloneable, TSerializable {
     private int version;
     private Object[] array;
     private int head;
@@ -38,8 +39,8 @@ public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>
         } else {
             array = new Object[c.size() + 1];
             int index = 0;
-            for (TIterator<? extends E> iter = c.iterator(); iter.hasNext();) {
-                array[index++] = iter.next();
+            for (var it = c.iterator(); it.hasNext();) {
+                array[index++] = it.next();
             }
             tail = array.length - 1;
         }
@@ -47,28 +48,19 @@ public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>
 
     @Override
     public void addFirst(E e) {
-        if (e == null) {
-            throw new TNullPointerException();
-        }
+        TObjects.requireNonNull(e);
         ensureCapacity(size() + 1);
-        --head;
-        if (head < 0) {
-            head += array.length;
-        }
+        head = modDec(head, array.length);
         array[head] = e;
         ++version;
     }
 
     @Override
     public void addLast(E e) {
-        if (e == null) {
-            throw new TNullPointerException();
-        }
+        TObjects.requireNonNull(e);
         ensureCapacity(size() + 1);
-        array[tail++] = e;
-        if (tail >= array.length) {
-            tail = 0;
-        }
+        array[tail] = e;
+        tail = modInc(tail, array.length);
         ++version;
     }
 
@@ -110,10 +102,7 @@ public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>
         @SuppressWarnings("unchecked")
         E result = (E) array[head];
         array[head] = null;
-        head++;
-        if (head >= array.length) {
-            head = 0;
-        }
+        head = modInc(head, array.length);
         ++version;
         return result;
     }
@@ -123,10 +112,7 @@ public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>
         if (head == tail) {
             return null;
         }
-        --tail;
-        if (tail < 0) {
-            tail = array.length - 1;
-        }
+        tail = modDec(tail, array.length);
         @SuppressWarnings("unchecked")
         E result = (E) array[tail];
         array[tail] = null;
@@ -161,7 +147,7 @@ public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>
     @Override
     @SuppressWarnings("unchecked")
     public E peekLast() {
-        return !isEmpty() ? (E) array[tail > 0 ? tail - 1 : array.length - 1] : null;
+        return !isEmpty() ? (E) array[modDec(tail, array.length)] : null;
     }
 
     @Override
@@ -169,9 +155,9 @@ public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>
         if (o == null) {
             return false;
         }
-        for (TIterator<E> iter = iterator(); iter.hasNext();) {
-            if (iter.next().equals(o)) {
-                iter.remove();
+        for (var it = iterator(); it.hasNext();) {
+            if (it.next().equals(o)) {
+                it.remove();
                 return true;
             }
         }
@@ -183,9 +169,9 @@ public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>
         if (o == null) {
             return false;
         }
-        for (TIterator<E> iter = descendingIterator(); iter.hasNext();) {
-            if (iter.next().equals(o)) {
-                iter.remove();
+        for (var it = descendingIterator(); it.hasNext();) {
+            if (it.next().equals(o)) {
+                it.remove();
                 return true;
             }
         }
@@ -243,68 +229,85 @@ public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>
         return head == tail;
     }
 
-    private void removeAt(int index) {
+    private boolean removeAt(int index) {
         if (head < tail) {
             if (tail - index < index - head) {
                 for (int i = index + 1; i < tail; ++i) {
                     array[i - 1] = array[i];
                 }
                 array[--tail] = null;
+                return true;
             } else {
                 for (int i = index - 1; i >= head; --i) {
                     array[i + 1] = array[i];
                 }
                 array[head++] = null;
+                return false;
             }
         } else {
             if (index >= head) {
                 for (int i = index - 1; i >= head; --i) {
                     array[i + 1] = array[i];
                 }
-                array[head++] = null;
-                if (head >= array.length) {
-                    head = 0;
-                }
+                array[head] = null;
+                head = modInc(head, array.length);
+                return false;
             } else {
                 for (int i = index + 1; i < tail; ++i) {
                     array[i - 1] = array[i];
                 }
-                if (--tail < 0) {
-                    tail += array.length;
-                }
+                tail = modDec(tail, array.length);
                 array[tail] = null;
+                return true;
             }
         }
     }
 
+    private static int modInc(int i, int mod) {
+        return ++i == mod ? 0 : i;
+    }
+
+    private static int modDec(int i, int mod) {
+        return --i == -1 ? mod - 1 : i;
+    }
+
     @Override
     public TIterator<E> iterator() {
-        return new TIterator<E>() {
+        return new TIterator<>() {
             private int refVersion = version;
             private int index = head;
             private int lastIndex = -1;
-            private boolean wrapped = head <= tail;
-            @Override public boolean hasNext() {
-                return !wrapped || index < tail;
+            private int left = size();
+
+            @Override
+            public boolean hasNext() {
+                return left > 0;
+            }
+
+            @Override
+            public E next() {
+                if (--left < 0) {
+                    throw new TNoSuchElementException();
                 }
-            @Override public E next() {
                 if (version > refVersion) {
                     throw new TConcurrentModificationException();
                 }
                 lastIndex = index;
                 @SuppressWarnings("unchecked")
-                E result = (E) array[index++];
-                if (index >= array.length) {
-                    index = 0;
-                    wrapped = true;
-                }
+                E result = (E) array[index];
+                index = modInc(index, array.length);
                 return result;
             }
-            @Override public void remove() {
+
+            @Override
+            public void remove() {
                 if (lastIndex < 0) {
                     throw new IllegalStateException();
                 }
-                removeAt(lastIndex);
+                boolean toLeft = removeAt(lastIndex);
+                if (toLeft) {
+                    index = modInc(index, array.length);
+                }
                 lastIndex = -1;
             }
         };
@@ -312,30 +315,41 @@ public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>
 
     @Override
     public TIterator<E> descendingIterator() {
-        return new TIterator<E>() {
+        return new TIterator<>() {
             private int refVersion = version;
             private int index = tail;
             private int lastIndex = -1;
-            private boolean wrapped = head <= tail;
-            @Override public boolean hasNext() {
-                return !wrapped || index > head;
+            private int left = size();
+
+            @Override
+            public boolean hasNext() {
+                return left > 0;
+            }
+
+            @Override
+            public E next() {
+                if (--left < 0) {
+                    throw new TNoSuchElementException();
                 }
-            @Override public E next() {
                 if (version > refVersion) {
                     throw new TConcurrentModificationException();
                 }
-                --index;
-                if (index < 0) {
-                    index = array.length - 1;
-                    wrapped = true;
-                }
+                index = modDec(index, array.length);
                 lastIndex = index;
                 @SuppressWarnings("unchecked")
                 E result = (E) array[index];
                 return result;
             }
-            @Override public void remove() {
-                removeAt(lastIndex);
+
+            @Override
+            public void remove() {
+                if (lastIndex < 0) {
+                    throw new IllegalStateException();
+                }
+                boolean toLeft = removeAt(lastIndex);
+                if (!toLeft) {
+                    index = modInc(index, array.length);
+                }
                 lastIndex = -1;
             }
         };
@@ -345,9 +359,9 @@ public class TArrayDeque<E> extends TAbstractCollection<E> implements TDeque<E>
         if (capacity < array.length) {
             return;
         }
-        int newArraySize = TMath.max(array.length * 2, capacity * 3 / 2 + 1);
+        int newArraySize = Math.max(array.length * 2, capacity * 3 / 2 + 1);
         if (newArraySize < 1) {
-            newArraySize = TInteger.MAX_VALUE;
+            newArraySize = Integer.MAX_VALUE;
         }
         Object[] newArray = new Object[newArraySize];
         int j = 0;

classlib/src/main/java/org/teavm/classlib/java/util/TDeque.java

@@ -16,31 +16,18 @@
 package org.teavm.classlib.java.util;
 
 /**
- *
- * @author Alexey Andreev
  * @param <E>
+ * @author Alexey Andreev
  */
-public interface TDeque<E> extends TQueue<E> {
-    void addFirst(E e);
-
-    void addLast(E e);
-
+public interface TDeque<E> extends TQueue<E>, TSequencedCollection<E> {
     boolean offerFirst(E e);
 
     boolean offerLast(E e);
 
-    E removeFirst();
-
-    E removeLast();
-
     E pollFirst();
 
     E pollLast();
 
-    E getFirst();
-
-    E getLast();
-
     E peekFirst();
 
     E peekLast();
@@ -54,4 +41,9 @@ public interface TDeque<E> extends TQueue<E> {
     E pop();
 
     TIterator<E> descendingIterator();
+
+    @Override
+    default TDeque<E> reversed() {
+        return new TReversedDeque<>(this);
+    }
 }

classlib/src/main/java/org/teavm/classlib/java/util/TReversedDeque.java

@@ -0,0 +1,253 @@
+/*
+ *  Copyright 2023 ihromant.
+ *
+ *  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 org.teavm.classlib.java.util;
+
+import java.lang.reflect.Array;
+
+class TReversedDeque<E> implements TDeque<E> {
+    private final TDeque<E> base;
+
+    TReversedDeque(TDeque<E> base) {
+        this.base = base;
+    }
+
+    @Override
+    public TDeque<E> reversed() {
+        return base;
+    }
+
+    @Override
+    public TIterator<E> iterator() {
+        return base.descendingIterator();
+    }
+
+    @Override
+    public int size() {
+        return base.size();
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return base.isEmpty();
+    }
+
+    @Override
+    public boolean contains(Object o) {
+        return base.contains(o);
+    }
+
+    @Override
+    public Object[] toArray() {
+        Object[] arr = new Object[size()];
+        int i = 0;
+        for (var it = base.descendingIterator(); it.hasNext();) {
+            arr[i++] = it.next();
+        }
+        return arr;
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public <T> T[] toArray(T[] a) {
+        int size = size();
+        if (a.length < size) {
+            a = (T[]) Array.newInstance(a.getClass().getComponentType(), size);
+        } else {
+            for (int i = size; i < a.length; ++i) {
+                a[i] = null;
+            }
+        }
+        int i = 0;
+        for (var it = base.descendingIterator(); it.hasNext();) {
+            a[i++] = (T) it.next();
+        }
+        return a;
+    }
+
+    @Override
+    public boolean add(E e) {
+        base.addFirst(e);
+        return true;
+    }
+
+    @Override
+    public void addFirst(E e) {
+        base.addLast(e);
+    }
+
+    @Override
+    public void addLast(E e) {
+        base.addFirst(e);
+    }
+
+    @Override
+    public boolean remove(Object o) {
+        for (var it = base.descendingIterator(); it.hasNext();) {
+            E e = it.next();
+            if (TObjects.equals(e, o)) {
+                it.remove();
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public boolean containsAll(TCollection<?> c) {
+        return base.contains(c);
+    }
+
+    @Override
+    public boolean addAll(TCollection<? extends E> c) {
+        boolean changed = false;
+        for (var it = c.iterator(); it.hasNext();) {
+            addFirst(it.next());
+            changed = true;
+        }
+        return changed;
+    }
+
+    @Override
+    public boolean removeAll(TCollection<?> c) {
+        boolean changed = false;
+        for (var it = base.descendingIterator(); it.hasNext();) {
+            E e = it.next();
+            if (c.contains(e)) {
+                it.remove();
+                changed = true;
+            }
+        }
+        return changed;
+    }
+
+    @Override
+    public boolean retainAll(TCollection<?> c) {
+        boolean changed = false;
+        for (var it = base.descendingIterator(); it.hasNext();) {
+            E e = it.next();
+            if (!c.contains(e)) {
+                it.remove();
+                changed = true;
+            }
+        }
+        return changed;
+    }
+
+    @Override
+    public void clear() {
+        base.clear();
+    }
+
+    @Override
+    public boolean offerFirst(E e) {
+        return base.offerLast(e);
+    }
+
+    @Override
+    public boolean offerLast(E e) {
+        return base.offerFirst(e);
+    }
+
+    @Override
+    public E pollFirst() {
+        return base.pollLast();
+    }
+
+    @Override
+    public E pollLast() {
+        return base.pollFirst();
+    }
+
+    @Override
+    public E peekFirst() {
+        return base.peekLast();
+    }
+
+    @Override
+    public E peekLast() {
+        return base.peekFirst();
+    }
+
+    @Override
+    public boolean removeFirstOccurrence(Object o) {
+        return base.removeLastOccurrence(o);
+    }
+
+    @Override
+    public boolean removeLastOccurrence(Object o) {
+        return base.removeFirstOccurrence(o);
+    }
+
+    @Override
+    public void push(E e) {
+        base.addLast(e);
+    }
+
+    @Override
+    public E pop() {
+        return base.removeLast();
+    }
+
+    @Override
+    public TIterator<E> descendingIterator() {
+        return base.iterator();
+    }
+
+    @Override
+    public boolean offer(E e) {
+        return base.offerFirst(e);
+    }
+
+    @Override
+    public E remove() {
+        return base.removeLast();
+    }
+
+    @Override
+    public E removeFirst() {
+        return base.removeLast();
+    }
+
+    @Override
+    public E removeLast() {
+        return base.removeFirst();
+    }
+
+    @Override
+    public E poll() {
+        return base.pollLast();
+    }
+
+    @Override
+    public E element() {
+        return base.getLast();
+    }
+
+    @Override
+    public E getFirst() {
+        return base.getLast();
+    }
+
+    @Override
+    public E getLast() {
+        return base.getFirst();
+    }
+
+    @Override
+    public E peek() {
+        return base.peekLast();
+    }
+}

tests/src/test/java/org/teavm/classlib/java/util/ArrayDequeTest.java

@@ -15,12 +15,16 @@
  */
 package org.teavm.classlib.java.util;
 
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 import java.util.ArrayDeque;
 import java.util.Deque;
 import java.util.Iterator;
-import org.junit.Assert;
+import java.util.List;
+import java.util.NoSuchElementException;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.teavm.junit.TeaVMTestRunner;
@@ -137,19 +141,19 @@ public class ArrayDequeTest {
         Object object2 = new Object();
         Object object3 = new Object();
         arrayDeque.add(object1);
-        Assert.assertTrue(arrayDeque.size() == 1);
+        assertEquals(1, arrayDeque.size());
         arrayDeque.remove(object1);
-        Assert.assertTrue(arrayDeque.size() == 0);
+        assertEquals(0, arrayDeque.size());
         arrayDeque.add(object1);
         arrayDeque.add(object2);
         arrayDeque.add(object3);
-        Assert.assertTrue(arrayDeque.size() == 3);
+        assertEquals(3, arrayDeque.size());
         arrayDeque.remove(object1);
         arrayDeque.remove(object2);
         arrayDeque.remove(object3);
-        Assert.assertTrue(arrayDeque.size() == 0);
+        assertEquals(0, arrayDeque.size());
         arrayDeque.remove(object1);
-        Assert.assertTrue(arrayDeque.size() == 0);
+        assertEquals(0, arrayDeque.size());
     }
 
     @Test
@@ -162,9 +166,9 @@ public class ArrayDequeTest {
         arrayDeque1.add(object2);
         arrayDeque1.add(object3);
         arrayDeque1.removeFirst();
-        Assert.assertTrue(arrayDeque1.size() == 2);
-        Assert.assertTrue(arrayDeque1.contains(object2));
-        Assert.assertTrue(arrayDeque1.contains(object3));
+        assertEquals(2, arrayDeque1.size());
+        assertTrue(arrayDeque1.contains(object2));
+        assertTrue(arrayDeque1.contains(object3));
 
         ArrayDeque<Object> arrayDeque2 = new ArrayDeque<>();
         arrayDeque2.add(object1);
@@ -172,8 +176,8 @@ public class ArrayDequeTest {
         arrayDeque2.add(object3);
         arrayDeque2.remove(object1);
         arrayDeque2.removeFirst();
-        Assert.assertTrue(arrayDeque2.size() == 1);
-        Assert.assertTrue(arrayDeque2.contains(object3));
+        assertEquals(1, arrayDeque2.size());
+        assertTrue(arrayDeque2.contains(object3));
 
         ArrayDeque<Object> arrayDeque3 = new ArrayDeque<>();
         arrayDeque3.add(object1);
@@ -181,8 +185,8 @@ public class ArrayDequeTest {
         arrayDeque3.add(object3);
         arrayDeque3.remove(object2);
         arrayDeque3.removeFirst();
-        Assert.assertTrue(arrayDeque3.size() == 1);
-        Assert.assertTrue(arrayDeque3.contains(object3));
+        assertEquals(1, arrayDeque3.size());
+        assertTrue(arrayDeque3.contains(object3));
 
         ArrayDeque<Object> arrayDeque4 = new ArrayDeque<>();
         arrayDeque4.add(object1);
@@ -190,8 +194,8 @@ public class ArrayDequeTest {
         arrayDeque4.add(object3);
         arrayDeque4.remove(object3);
         arrayDeque4.removeFirst();
-        Assert.assertTrue(arrayDeque4.size() == 1);
-        Assert.assertTrue(arrayDeque4.contains(object2));
+        assertEquals(1, arrayDeque4.size());
+        assertTrue(arrayDeque4.contains(object2));
     }
 
     @Test
@@ -204,9 +208,9 @@ public class ArrayDequeTest {
         arrayDeque1.add(object2);
         arrayDeque1.add(object3);
         arrayDeque1.removeLast();
-        Assert.assertTrue(arrayDeque1.size() == 2);
-        Assert.assertTrue(arrayDeque1.contains(object1));
-        Assert.assertTrue(arrayDeque1.contains(object2));
+        assertEquals(2, arrayDeque1.size());
+        assertTrue(arrayDeque1.contains(object1));
+        assertTrue(arrayDeque1.contains(object2));
 
         ArrayDeque<Object> arrayDeque2 = new ArrayDeque<>();
         arrayDeque2.add(object1);
@@ -214,8 +218,8 @@ public class ArrayDequeTest {
         arrayDeque2.add(object3);
         arrayDeque2.remove(object3);
         arrayDeque2.removeLast();
-        Assert.assertTrue(arrayDeque2.size() == 1);
-        Assert.assertTrue(arrayDeque2.contains(object1));
+        assertEquals(1, arrayDeque2.size());
+        assertTrue(arrayDeque2.contains(object1));
 
         ArrayDeque<Object> arrayDeque3 = new ArrayDeque<>();
         arrayDeque3.add(object1);
@@ -223,8 +227,8 @@ public class ArrayDequeTest {
         arrayDeque3.add(object3);
         arrayDeque3.remove(object2);
         arrayDeque3.removeLast();
-        Assert.assertTrue(arrayDeque3.size() == 1);
-        Assert.assertTrue(arrayDeque3.contains(object1));
+        assertEquals(1, arrayDeque3.size());
+        assertTrue(arrayDeque3.contains(object1));
 
         ArrayDeque<Object> arrayDeque4 = new ArrayDeque<>();
         arrayDeque4.add(object1);
@@ -232,8 +236,8 @@ public class ArrayDequeTest {
         arrayDeque4.add(object3);
         arrayDeque4.remove(object3);
         arrayDeque4.removeLast();
-        Assert.assertTrue(arrayDeque4.size() == 1);
-        Assert.assertTrue(arrayDeque4.contains(object1));
+        assertEquals(1, arrayDeque4.size());
+        assertTrue(arrayDeque4.contains(object1));
     }
 
     @Test
@@ -254,4 +258,115 @@ public class ArrayDequeTest {
             arrayDeque.removeLast();
         }
     }
+
+    @Test
+    public void testSequencedCollectionReadOnly() {
+        Deque<String> deque = new ArrayDeque<>(List.of("0", "1", "2", "3", "4", "5", "6"));
+        Deque<String> reversed = deque.reversed();
+        Iterator<String> it = reversed.iterator();
+        assertEquals("6", it.next());
+        assertEquals("5", it.next());
+        assertEquals("6", reversed.getFirst());
+        assertEquals("0", reversed.getLast());
+        assertEquals("6", reversed.peek());
+        assertEquals("6", reversed.peekFirst());
+        assertEquals("0", reversed.peekLast());
+    }
+
+    @Test
+    public void testSequencedCollectionMutations() {
+        Deque<String> deque = new ArrayDeque<>(List.of("a", "b", "c", "d"));
+        assertEquals("a", deque.removeFirst());
+        assertEquals("d", deque.removeLast());
+        deque.addFirst("u");
+        deque.addLast("e");
+        assertArrayEquals(new String[] { "u", "b", "c", "e" }, deque.toArray());
+        deque = new ArrayDeque<>(List.of("a", "b", "c", "d")).reversed();
+        assertEquals("d", deque.removeFirst());
+        assertEquals("a", deque.removeLast());
+        deque.addFirst("u");
+        deque.addLast("e");
+        assertEquals("u", deque.remove());
+        deque.add("f");
+        assertArrayEquals(new String[] { "c", "b", "e", "f" }, deque.toArray());
+    }
+
+    @Test
+    public void testSequencedCollectionIterator() {
+        Deque<String> deque = new ArrayDeque<>(List.of("a", "b", "c", "d"));
+        deque.addLast("e");
+        deque.addLast("f");
+        Iterator<String> it = deque.iterator();
+        assertEquals("a", it.next());
+        it.remove();
+        assertEquals("b", it.next());
+        it.remove();
+        assertEquals("c", it.next());
+        it.remove();
+        assertEquals("d", it.next());
+        it.remove();
+        assertEquals("e", it.next());
+        it.remove();
+        assertEquals("f", it.next());
+        it.remove();
+        assertTrue(deque.isEmpty());
+        try {
+            it.next();
+            fail();
+        } catch (NoSuchElementException e) {
+            // ok
+        }
+        deque = new ArrayDeque<>(List.of("a", "b", "c", "d")).reversed();
+        it = deque.iterator();
+        assertEquals("d", it.next());
+        assertEquals("c", it.next());
+        it.remove();
+        assertArrayEquals(new String[] { "d", "b", "a" }, deque.toArray());
+        deque = new ArrayDeque<>(List.of("a", "b", "c", "d")).reversed();
+        it = deque.iterator();
+        assertEquals("d", it.next());
+        assertEquals("c", it.next());
+        it.remove();
+        assertEquals("b", it.next());
+        it.remove();
+        assertEquals("a", it.next());
+        try {
+            it.next();
+            fail();
+        } catch (NoSuchElementException e) {
+            // ok
+        }
+        assertArrayEquals(new String[] { "d", "a" }, deque.toArray());
+    }
+
+    @Test
+    public void sequenceCollectionMethodsOnEmpty() {
+        var empty = new ArrayDeque<>();
+
+        try {
+            empty.getFirst();
+            fail();
+        } catch (NoSuchElementException e) {
+            // ok
+        }
+        try {
+            empty.getLast();
+            fail();
+        } catch (NoSuchElementException e) {
+            // ok
+        }
+
+        try {
+            empty.removeFirst();
+            fail();
+        } catch (NoSuchElementException e) {
+            // ok
+        }
+        try {
+            empty.removeLast();
+            fail();
+        } catch (NoSuchElementException e) {
+            // ok
+        }
+    }
 }