From 35045dd0fadca87152d346d81ba7d0523351e48f Mon Sep 17 00:00:00 2001
From: Tobias Jordine <jordine@hdm-stuttgart.de>
Date: Tue, 14 Jun 2022 21:30:38 +0200
Subject: [PATCH] Vorlesung 13.06.2022
---
.../concurrency/issues/BlockingQueue.java | 80 +++++++++++++++++++
.../concurrency/issues/LostUpdate.java | 13 ++-
.../solutions/LostUpdateSynchronized.java | 15 ++--
website/index.html | 1 +
4 files changed, 100 insertions(+), 9 deletions(-)
create mode 100644 src/main/java/de/hdm/jordine/vorlesung/concurrency/issues/BlockingQueue.java
diff --git a/src/main/java/de/hdm/jordine/vorlesung/concurrency/issues/BlockingQueue.java b/src/main/java/de/hdm/jordine/vorlesung/concurrency/issues/BlockingQueue.java
new file mode 100644
index 0000000..ddf41a1
--- /dev/null
+++ b/src/main/java/de/hdm/jordine/vorlesung/concurrency/issues/BlockingQueue.java
@@ -0,0 +1,80 @@
+package de.hdm.jordine.vorlesung.concurrency.issues;
+
+import java.util.LinkedList;
+import java.util.Queue;
+
+ public class BlockingQueue<T> {
+ private Queue<T> queue = new LinkedList<T>();
+ private int capacity;
+ public BlockingQueue(int capacity) {
+ this.capacity = capacity;
+ }
+ public synchronized void put(T element) throws InterruptedException {
+ while(queue.size() == capacity) {
+ System.out.println("waitng to add");
+ wait();
+
+ }
+ queue.add(element);
+ notify(); // notifyAll() for multiple producer/consumer threads
+ }
+ public synchronized T take() throws InterruptedException {
+ while(queue.isEmpty()) {
+ System.out.println("waitng to remove");
+ wait();
+ }
+ T item = queue.remove();
+ notify(); // notifyAll() for multiple producer/consumer threads
+ return item;
+ }
+
+ public static void main(String[] args) {
+
+
+ BlockingQueue<String> b = new BlockingQueue<>(1);
+
+ Thread t0 = new Thread(new Runnable() {
+ @Override
+ public void run() {
+ try {
+ b.put("Hello");
+ System.out.println("adding hello");
+ } catch (InterruptedException e) {
+ e.printStackTrace();
+ }
+ }
+ });
+
+ t0.start();
+
+ Thread t1 = new Thread(new Runnable() {
+ @Override
+ public void run() {
+ try {
+ b.put("World");
+ System.out.println("adding World");
+ } catch (InterruptedException e) {
+ e.printStackTrace();
+ }
+ }
+ });
+
+ t1.start();
+
+ Thread t2 = new Thread(new Runnable() {
+ @Override
+ public void run() {
+ try {
+ String text = b.take();
+ System.out.println("removing " + text);
+ } catch (InterruptedException e) {
+ e.printStackTrace();
+ }
+ }
+ });
+
+ t2.start();
+
+ }
+ }
+
diff --git a/src/main/java/de/hdm/jordine/vorlesung/concurrency/issues/LostUpdate.java b/src/main/java/de/hdm/jordine/vorlesung/concurrency/issues/LostUpdate.java
index 5c3d45d..8aa155c 100644
--- a/src/main/java/de/hdm/jordine/vorlesung/concurrency/issues/LostUpdate.java
+++ b/src/main/java/de/hdm/jordine/vorlesung/concurrency/issues/LostUpdate.java
@@ -2,10 +2,11 @@ package de.hdm.jordine.vorlesung.concurrency.issues;
public class LostUpdate {
+ //private volatile int counter = 0;
private int counter = 0;
public void increment(){
- counter++;
+ counter = counter + 1;
}
public static void main(String[] args) throws InterruptedException {
@@ -30,13 +31,19 @@ public class LostUpdate {
}
});
+ long start = System.currentTimeMillis();
+
t0.start();
t1.start();
- //t0.join();
- //t1.join();
+ // t0.join(); // required for synchronisation with main thread
+ // t1.join(); // required for synchronisation with main thread
+
+ long end = System.currentTimeMillis();
System.out.println("Counter value: " + lu.counter);
+
+ System.out.println(end - start);
}
diff --git a/src/main/java/de/hdm/jordine/vorlesung/concurrency/solutions/LostUpdateSynchronized.java b/src/main/java/de/hdm/jordine/vorlesung/concurrency/solutions/LostUpdateSynchronized.java
index d2929ca..05bc071 100644
--- a/src/main/java/de/hdm/jordine/vorlesung/concurrency/solutions/LostUpdateSynchronized.java
+++ b/src/main/java/de/hdm/jordine/vorlesung/concurrency/solutions/LostUpdateSynchronized.java
@@ -4,15 +4,12 @@ public class LostUpdateSynchronized {
private int counter = 0;
- public void increment(){
+ public synchronized void increment(){
counter++;
}
public static void main(String[] args) throws InterruptedException {
- Object monitor0 = new Object();
- Object monitor1 = new Object();
-
LostUpdateSynchronized lu = new LostUpdateSynchronized();
Thread t0 = new Thread(new Runnable() {
@@ -33,13 +30,19 @@ public class LostUpdateSynchronized {
}
});
+ long start = System.currentTimeMillis();
+
t0.start();
t1.start();
- //t0.join();
- //t1.join();
+ t0.join(); // required for synchronisation with main thread
+ t1.join(); // required for synchronisation with main thread
+
+ long end = System.currentTimeMillis();
System.out.println("Counter value: " + lu.counter);
+
+ System.out.println(end - start);
}
diff --git a/website/index.html b/website/index.html
index 0af7d67..34c9fd2 100644
--- a/website/index.html
+++ b/website/index.html
@@ -71,6 +71,7 @@
<li><a href="https://bigbluebutton.hdm-stuttgart.de/playback/presentation/2.3/cf93de2bb79bc2a9a9374f2f59a28fe89d96716b-1652709634577" target="_blank">16.05.: CI/CD, SQL</a></li>
<li><a href="https://bigbluebutton.hdm-stuttgart.de/playback/presentation/2.3/cf93de2bb79bc2a9a9374f2f59a28fe89d96716b-1653313987460" target="_blank">23.05.: SQL, NoSQL, Schnittstellen</a></li>
<li><a href="https://bigbluebutton.hdm-stuttgart.de/playback/presentation/2.3/cf93de2bb79bc2a9a9374f2f59a28fe89d96716b-1653940765288" target="_blank">30.05.: Schnittstellen (Nachaufzeichnung)</a></li>
+ <li><a href="https://bigbluebutton.hdm-stuttgart.de/playback/presentation/2.3/cf93de2bb79bc2a9a9374f2f59a28fe89d96716b-1655128617403" target="_blank">13.06.: Parallele Programmierung</a></li>
</ul>
<h4>Tafelbilder</h4>
--
GitLab