BAEL-519 Introduction to LMAX Disruptor (#948)

* BAL-36 File size api in java and apache commons IO

* BAEL-282 grep in java - fixes after code review

* BAEL-519 Added support for disruptor library

* BAEL-519 Added support for disruptor library

* BAEL-519 Added support for disruptor library

* BAEL-519 Added support for disruptor library

* BAEL-519 Added support for disruptor library

* BAEL-519 Added support for disruptor library

* BAEL-519 Added support for disruptor

* BAEL-519 Moved all supporting classes to main source

* BAEL-519 Moved all supporting classes to main source

* BAEL-519 Moved asserts and test classes in test folder.

* BAEL-519 moved test related producer and consumer to src.

* BAEL-586 Guide to Guava BiMap.

* BAEL-587 formatted code.

* BAEL-519 LMAX Disruptor

* BAEL-587 resolved merge

* BAEL-587 Resolved merge

* BAEL-519 Removed disruptor link.

* BAEL-519 Reverted Guava changes

core-java/src/test/java/com/baeldung/disruptor/DisruptorTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.disruptor;
+
+import java.util.concurrent.ThreadFactory;
+import org.junit.Before;
+import org.junit.Test;
+import com.lmax.disruptor.BusySpinWaitStrategy;
+import com.lmax.disruptor.RingBuffer;
+import com.lmax.disruptor.WaitStrategy;
+import com.lmax.disruptor.dsl.Disruptor;
+import com.lmax.disruptor.dsl.ProducerType;
+import com.lmax.disruptor.util.DaemonThreadFactory;
+
+public class DisruptorTest {
+    private Disruptor<ValueEvent> disruptor;
+    private WaitStrategy waitStrategy;
+
+    @Before
+    public void setUp() throws Exception {
+        waitStrategy = new BusySpinWaitStrategy();
+    }
+
+    private void createDisruptor(final ProducerType producerType, final EventConsumer eventConsumer) {
+        final ThreadFactory threadFactory = DaemonThreadFactory.INSTANCE;
+        disruptor = new Disruptor<ValueEvent>(ValueEvent.EVENT_FACTORY, 16, threadFactory, producerType, waitStrategy);
+        disruptor.handleEventsWith(eventConsumer.getEventHandler());
+    }
+
+    private void startProducing(final RingBuffer<ValueEvent> ringBuffer, final int count, final EventProducer eventProducer) {
+        eventProducer.startProducing(ringBuffer, count);
+    }
+
+    @Test
+    public void whenMultipleProducerSingleConsumer_thenOutputInFifoOrder() {
+        final EventConsumer eventConsumer = new SingleEventPrintConsumer();
+        final EventProducer eventProducer = new DelayedMultiEventProducer();
+        createDisruptor(ProducerType.MULTI, eventConsumer);
+        final RingBuffer<ValueEvent> ringBuffer = disruptor.start();
+
+        startProducing(ringBuffer, 32, eventProducer);
+
+        disruptor.halt();
+        disruptor.shutdown();
+    }
+
+    @Test
+    public void whenSingleProducerSingleConsumer_thenOutputInFifoOrder() {
+        final EventConsumer eventConsumer = new SingleEventConsumer();
+        final EventProducer eventProducer = new SingleEventProducer();
+        createDisruptor(ProducerType.SINGLE, eventConsumer);
+        final RingBuffer<ValueEvent> ringBuffer = disruptor.start();
+
+        startProducing(ringBuffer, 32, eventProducer);
+
+        disruptor.halt();
+        disruptor.shutdown();
+    }
+
+    @Test
+    public void whenSingleProducerMultipleConsumer_thenOutputInFifoOrder() {
+        final EventConsumer eventConsumer = new MultiEventConsumer();
+        final EventProducer eventProducer = new SingleEventProducer();
+        createDisruptor(ProducerType.SINGLE, eventConsumer);
+        final RingBuffer<ValueEvent> ringBuffer = disruptor.start();
+
+        startProducing(ringBuffer, 32, eventProducer);
+
+        disruptor.halt();
+        disruptor.shutdown();
+    }
+
+    @Test
+    public void whenMultipleProducerMultipleConsumer_thenOutputInFifoOrder() {
+        final EventConsumer eventConsumer = new MultiEventPrintConsumer();
+        final EventProducer eventProducer = new DelayedMultiEventProducer();
+        createDisruptor(ProducerType.MULTI, eventConsumer);
+        final RingBuffer<ValueEvent> ringBuffer = disruptor.start();
+
+        startProducing(ringBuffer, 32, eventProducer);
+
+        disruptor.halt();
+        disruptor.shutdown();
+    }
+}

core-java/src/test/java/com/baeldung/disruptor/MultiEventConsumer.java

@@ -0,0 +1,27 @@
+package com.baeldung.disruptor;
+
+import static org.junit.Assert.assertEquals;
+
+import com.lmax.disruptor.EventHandler;
+
+public class MultiEventConsumer implements EventConsumer {
+
+    private int expectedValue = -1;
+    private int otherExpectedValue = -1;
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public EventHandler<ValueEvent>[] getEventHandler() {
+        final EventHandler<ValueEvent> eventHandler = (event, sequence, endOfBatch) -> assertExpectedValue(event.getValue());
+        final EventHandler<ValueEvent> otherEventHandler = (event, sequence, endOfBatch) -> assertOtherExpectedValue(event.getValue());
+        return new EventHandler[] { eventHandler, otherEventHandler };
+    }
+
+    private void assertExpectedValue(final int id) {
+        assertEquals(++expectedValue, id);
+    }
+
+    private void assertOtherExpectedValue(final int id) {
+        assertEquals(++otherExpectedValue, id);
+    }
+}

core-java/src/test/java/com/baeldung/disruptor/SingleEventConsumer.java

@@ -0,0 +1,21 @@
+package com.baeldung.disruptor;
+
+import static org.junit.Assert.assertEquals;
+
+import com.lmax.disruptor.EventHandler;
+
+public class SingleEventConsumer implements EventConsumer {
+
+    private int expectedValue = -1;
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public EventHandler<ValueEvent>[] getEventHandler() {
+        final EventHandler<ValueEvent> eventHandler = (event, sequence, endOfBatch) -> assertExpectedValue(event.getValue());
+        return new EventHandler[] { eventHandler };
+    }
+
+    private void assertExpectedValue(final int id) {
+        assertEquals(++expectedValue, id);
+    }
+}