Initial commit of guarded suspension design pattern

guarded-suspension/src/main/java/com/iluwatar/guarded/suspension/GuardedQueue.java

@@ -0,0 +1,66 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * 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 NONINFRINGEMENT. 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 com.iluwatar.guarded.suspension;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.LinkedList;
+import java.util.Queue;
+
+
+
+public class GuardedQueue {
+  private static final Logger LOGGER = LoggerFactory.getLogger(GuardedQueue.class);
+  private Queue<Integer> sourceList;
+
+  public GuardedQueue() {
+    this.sourceList = new LinkedList<>();
+  }
+
+  /**
+   * @return last element of a queue if queue is not empty
+   */
+  public synchronized Integer get() {
+    while (sourceList.isEmpty()) {
+      try {
+        LOGGER.info("waiting");
+        wait();
+      } catch (InterruptedException e) {
+        e.printStackTrace();
+      }
+    }
+
+    return sourceList.peek();
+  }
+
+  /**
+   * @param e number which we want to put to our queue
+   */
+  public synchronized void put(Integer e) {
+    sourceList.add(e);
+    notify();
+    LOGGER.info("notifying");
+
+  }
+}

guarded-suspension/src/test/java/com/iluwatar/guarded/suspension/GuardedQueueTest.java

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+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ * <p>
+ * 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:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * 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 NONINFRINGEMENT. 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 com.iluwatar.guarded.suspension;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Created by robertt240 on 1/2/17.
+ */
+public class GuardedQueueTest {
+  private volatile Integer value;
+
+  @Test
+  public void testGet() {
+    GuardedQueue g = new GuardedQueue();
+    ExecutorService executorService = Executors.newFixedThreadPool(2);
+    executorService.submit(() -> value = g.get());
+    executorService.submit(() -> g.put(Integer.valueOf(10)));
+    executorService.shutdown();
+    try {
+      executorService.awaitTermination(30, TimeUnit.SECONDS);
+    } catch (InterruptedException e) {
+      e.printStackTrace();
+    }
+    Assert.assertEquals(Integer.valueOf(10), value);
+  }
+
+}