Create AbstractForwardSequentialList util class

util/src/main/java/org/jf/util/AbstractForwardSequentialList.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2012, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.jf.util;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.AbstractSequentialList;
+import java.util.Iterator;
+import java.util.ListIterator;
+import java.util.NoSuchElementException;
+
+public abstract class AbstractForwardSequentialList<T> extends AbstractSequentialList<T> {
+
+    @Nonnull private Iterator<T> iterator(int index) {
+        if (index < 0) {
+            throw new NoSuchElementException();
+        }
+
+        Iterator<T> it = iterator();
+        for (int i=0; i<index; i++) {
+            it.next();
+        }
+        return it;
+    }
+
+    @Override @Nonnull public abstract Iterator<T> iterator();
+
+    @Override @Nonnull public ListIterator<T> listIterator(final int initialIndex) {
+
+        final Iterator<T> initialIterator;
+        try {
+            initialIterator = iterator(initialIndex);
+        } catch (NoSuchElementException ex) {
+            throw new IndexOutOfBoundsException();
+        }
+
+        return new AbstractListIterator<T>() {
+            private int index = initialIndex - 1;
+            @Nullable private Iterator<T> forwardIterator = initialIterator;
+
+            @Nonnull
+            private Iterator<T> getForwardIterator() {
+                if (forwardIterator == null) {
+                    try {
+                        forwardIterator = iterator(index+1);
+                    } catch (IndexOutOfBoundsException ex) {
+                        throw new NoSuchElementException();
+                    }
+                }
+                return forwardIterator;
+            }
+
+            @Override public boolean hasNext() {
+                return getForwardIterator().hasNext();
+            }
+
+            @Override public boolean hasPrevious() {
+                return index >= 0;
+            }
+
+            @Override public T next() {
+                T ret = getForwardIterator().next();
+                index++;
+                return ret;
+            }
+
+            @Override public int nextIndex() {
+                return index+1;
+            }
+
+            @Override public T previous() {
+                forwardIterator = null;
+                try {
+                    return iterator(index--).next();
+                } catch (IndexOutOfBoundsException ex) {
+                    throw new NoSuchElementException();
+                }
+            }
+
+            @Override public int previousIndex() {
+                return index;
+            }
+        };
+    }
+
+    @Override @Nonnull public ListIterator<T> listIterator() {
+        return listIterator(0);
+    }
+}

util/src/test/java/org/jf/util/AbstractForwardSequentialListTest.java

@@ -0,0 +1,214 @@
+/*
+ * Copyright 2012, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.jf.util;
+
+import junit.framework.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import javax.annotation.Nonnull;
+import java.util.Iterator;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.NoSuchElementException;
+
+public class AbstractForwardSequentialListTest {
+    private List<Integer> list;
+
+    @Before
+    public void setup() {
+        list = new AbstractForwardSequentialList<Integer>() {
+            @Nonnull @Override public Iterator<Integer> iterator() {
+                return new Iterator<Integer>() {
+                    private int index = 0;
+
+                    @Override public boolean hasNext() {
+                        return index < 100;
+                    }
+
+                    @Override public Integer next() {
+                        if (!hasNext()) {
+                            throw new NoSuchElementException();
+                        }
+                        return index++;
+                    }
+
+                    @Override public void remove() {
+                        throw new UnsupportedOperationException();
+                    }
+                };
+            }
+
+            @Override public int size() {
+                return 100;
+            }
+        };
+    }
+
+    private void testForwardIterationImpl(ListIterator<Integer> iter) {
+        Assert.assertFalse(iter.hasPrevious());
+
+        for (int i=0; i<100; i++) {
+            Assert.assertEquals(i, iter.nextIndex());
+            Assert.assertEquals(i-1, iter.previousIndex());
+
+            Assert.assertTrue(iter.hasNext());
+
+            Assert.assertEquals(i, iter.next().intValue());
+            Assert.assertTrue(iter.hasPrevious());
+        }
+
+        Assert.assertFalse(iter.hasNext());
+        Assert.assertEquals(iter.nextIndex(), 100);
+        Assert.assertEquals(iter.previousIndex(), 99);
+    }
+
+    @Test
+    public void testForwardIteration() {
+        testForwardIterationImpl(list.listIterator());
+    }
+
+    private void testReverseIterationImpl(ListIterator<Integer> iter) {
+        Assert.assertFalse(iter.hasNext());
+
+        for (int i=99; i>=0; i--) {
+            Assert.assertEquals(i+1, iter.nextIndex());
+            Assert.assertEquals(i, iter.previousIndex());
+
+            Assert.assertTrue(iter.hasPrevious());
+
+            Assert.assertEquals(i, iter.previous().intValue());
+            Assert.assertTrue(iter.hasNext());
+        }
+
+        Assert.assertFalse(iter.hasPrevious());
+        Assert.assertEquals(0, iter.nextIndex());
+        Assert.assertEquals(-1, iter.previousIndex());
+    }
+
+    @Test
+    public void testReverseIteration() {
+        testReverseIterationImpl(list.listIterator(100));
+    }
+
+    @Test
+    public void testAlternatingIteration() {
+        ListIterator<Integer> iter = list.listIterator(50);
+
+        for (int i=0; i<10; i++) {
+            Assert.assertTrue(iter.hasNext());
+            Assert.assertTrue(iter.hasPrevious());
+            Assert.assertEquals(50, iter.nextIndex());
+            Assert.assertEquals(49, iter.previousIndex());
+
+            Assert.assertEquals(50, iter.next().intValue());
+
+            Assert.assertTrue(iter.hasNext());
+            Assert.assertTrue(iter.hasPrevious());
+            Assert.assertEquals(51, iter.nextIndex());
+            Assert.assertEquals(50, iter.previousIndex());
+
+            Assert.assertEquals(50, iter.previous().intValue());
+        }
+    }
+
+    @Test
+    public void testAlternatingIteration2() {
+        ListIterator<Integer> iter = list.listIterator(0);
+
+        for (int i=0; i<10; i++) {
+            testForwardIterationImpl(iter);
+            testReverseIterationImpl(iter);
+        }
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void testNegativeIndex() {
+        list.listIterator(-1);
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void testLargeIndex() {
+        list.listIterator(101);
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void testLargeIndex2() {
+        list.listIterator(1000000);
+    }
+
+    @Test
+    public void testForwardIterationException() {
+        // note: no "expected = NoSuchElementException", because we want to make sure the exception occurs only during
+        // the last call to next()
+
+        ListIterator<Integer> iter = list.listIterator(0);
+        for (int i=0; i<100; i++) {
+            iter.next();
+        }
+        try {
+            iter.next();
+        } catch (NoSuchElementException ex) {
+            return;
+        }
+        Assert.fail();
+    }
+
+    @Test(expected = NoSuchElementException.class)
+    public void testForwardIterationException2() {
+        ListIterator<Integer> iter = list.listIterator(100);
+        iter.next();
+    }
+
+    @Test
+    public void testReverseIterationException() {
+        // note: no "expected = NoSuchElementException", because we want to make sure the exception occurs only during
+        // the last call to previous()
+
+        ListIterator<Integer> iter = list.listIterator(100);
+        for (int i=0; i<100; i++) {
+            iter.previous();
+        }
+        try {
+            iter.previous();
+        } catch (NoSuchElementException ex) {
+            return;
+        }
+        Assert.fail();
+    }
+
+    @Test(expected = NoSuchElementException.class)
+    public void testReverseIterationException2() {
+        ListIterator<Integer> iter = list.listIterator(0);
+        iter.previous();
+    }
+}