Add Semaphore example

winterbe · winterbe · commit 402225560d7e · 2015-04-12T07:34:23.000+02:00
diff --git a/src/com/winterbe/java8/samples/concurrent/Semaphore1.java b/src/com/winterbe/java8/samples/concurrent/Semaphore1.java
@@ -0,0 +1,51 @@
+package com.winterbe.java8.samples.concurrent;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+/**
+ * @author Benjamin Winterberg
+ */
+public class Semaphore1 {
+
+    private static final int NUM_INCREMENTS = 10000;
+
+    private static Semaphore semaphore = new Semaphore(1);
+
+    private static int count = 0;
+
+    public static void main(String[] args) {
+        testIncrement();
+    }
+
+    private static void testIncrement() {
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+
+        IntStream.range(0, NUM_INCREMENTS)
+                .forEach(i -> executor.submit(Semaphore1::increment));
+
+        ConcurrentUtils.stop(executor);
+
+        System.out.println("Increment: " + count);
+    }
+
+    private static void increment() {
+        boolean permit = false;
+        try {
+            permit = semaphore.tryAcquire(5, TimeUnit.SECONDS);
+            count++;
+        }
+        catch (InterruptedException e) {
+            throw new RuntimeException("could not increment");
+        }
+        finally {
+            if (permit) {
+                semaphore.release();
+            }
+        }
+    }
+
+}
diff --git a/src/com/winterbe/java8/samples/concurrent/Synchronized1.java b/src/com/winterbe/java8/samples/concurrent/Synchronized1.java
@@ -19,7 +19,7 @@ public static void main(String[] args) {
     }
 
     private static void testSyncIncrement() {
-        count = 1;
+        count = 0;
 
         ExecutorService executor = Executors.newFixedThreadPool(2);
 
@@ -32,7 +32,7 @@ private static void testSyncIncrement() {
     }
 
     private static void testNonSyncIncrement() {
-        count = 1;
+        count = 0;
 
         ExecutorService executor = Executors.newFixedThreadPool(2);
 
@@ -51,4 +51,5 @@ private static synchronized void incrementSync() {
     private static void increment() {
         count = count + 1;
     }
+
 }

Original file line number	Diff line number	Diff line change
`@@ -19,7 +19,7 @@ public static void main(String[] args) {`
`19`	`19`	`}`
`20`	`20`
`21`	`21`	`private static void testSyncIncrement() {`
`22`		`- count = 1;`
	`22`	`+ count = 0;`
`23`	`23`
`24`	`24`	`ExecutorService executor = Executors.newFixedThreadPool(2);`
`25`	`25`
`@@ -32,7 +32,7 @@ private static void testSyncIncrement() {`
`32`	`32`	`}`
`33`	`33`
`34`	`34`	`private static void testNonSyncIncrement() {`
`35`		`- count = 1;`
	`35`	`+ count = 0;`
`36`	`36`
`37`	`37`	`ExecutorService executor = Executors.newFixedThreadPool(2);`
`38`	`38`
`@@ -51,4 +51,5 @@ private static synchronized void incrementSync() {`
`51`	`51`	`private static void increment() {`
`52`	`52`	`count = count + 1;`
`53`	`53`	`}`
	`54`	`+`
`54`	`55`	`}`