Merge branch '__rultor'

src/main/java/org/cactoos/iterator/SyncIterator.java

@@ -0,0 +1,90 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2018 Yegor Bugayenko
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.cactoos.iterator;
+
+import java.util.Iterator;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+/**
+ * Synchronized {@link Iterator} implementation using a {@link ReadWriteLock}
+ * either provided to the constructor or an internally created
+ * {@link ReentrantReadWriteLock}.
+ * The {@link ReadWriteLock} is used to synchronize read calls to
+ * {@link SyncIterator#hasNext()} against write calls to
+ * {@link SyncIterator#next()} and write calls to any other read or write
+ * calls.
+ * @author Sven Diedrichsen (sven.diedrichsen@gmail.com)
+ * @version $Id$
+ * @param <T> The type of the iterator.
+ * @since 1.0
+ */
+public final class SyncIterator<T> implements Iterator<T> {
+    /**
+     * The original iterator.
+     */
+    private final Iterator<T> iterator;
+    /**
+     * The lock to use.
+     */
+    private final ReadWriteLock lock;
+
+    /**
+     * Ctor.
+     * @param iterator The iterator to synchronize access to.
+     */
+    public SyncIterator(final Iterator<T> iterator) {
+        this(iterator, new ReentrantReadWriteLock());
+    }
+
+    /**
+     * Ctor.
+     * @param iterator The iterator to synchronize access to.
+     * @param lock The lock to use for synchronization.
+     */
+    public SyncIterator(final Iterator<T> iterator, final ReadWriteLock lock) {
+        this.iterator = iterator;
+        this.lock = lock;
+    }
+
+    @Override
+    public boolean hasNext() {
+        this.lock.readLock().lock();
+        try {
+            return this.iterator.hasNext();
+        } finally {
+            this.lock.readLock().unlock();
+        }
+    }
+
+    @Override
+    public T next() {
+        this.lock.writeLock().lock();
+        try {
+            return this.iterator.next();
+        } finally {
+            this.lock.writeLock().unlock();
+        }
+    }
+}

src/test/java/org/cactoos/iterator/SyncIteratorTest.java

@@ -0,0 +1,76 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2018 Yegor Bugayenko
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.cactoos.iterator;
+
+import java.util.Arrays;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import org.cactoos.list.ListOf;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.Matchers;
+import org.junit.Test;
+
+// @todo #482:30min add multi-threaded tests which test that the lock syncs the
+//  access to the next method against next and hasNext calls and calls to the
+//  hasNext method against next calls.
+/**
+ * Test for {@link SyncIterator}.
+ *
+ * @author Sven Diedrichsen (sven.diedrichsen@gmail.com)
+ * @version $Id$
+ * @since 1.0
+ * @checkstyle JavadocMethodCheck (500 lines)
+ * @checkstyle MagicNumberCheck (500 lines)
+ * @checkstyle TodoCommentCheck (500 lines)
+ */
+@SuppressWarnings("PMD.AvoidDuplicateLiterals")
+public final class SyncIteratorTest {
+
+    @Test
+    public void syncIteratorReturnsCorrectValuesWithExternalLock() {
+        final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+        MatcherAssert.assertThat(
+            "Unexpected value found.",
+            new ListOf<>(
+                new SyncIterator<>(
+                    Arrays.asList("a", "b").iterator(), lock
+                )
+            ).toArray(),
+            Matchers.equalTo(new Object[]{"a", "b"})
+        );
+    }
+
+    @Test
+    public void syncIteratorReturnsCorrectValuesWithInternalLock() {
+        MatcherAssert.assertThat(
+            "Unexpected value found.",
+            new ListOf<>(
+                new SyncIterator<>(
+                    Arrays.asList("a", "b").iterator()
+                )
+            ).toArray(),
+            Matchers.equalTo(new Object[]{"a", "b"})
+        );
+    }
+
+}