code snippets of U3

.gitignore

+
+# Created by https://www.toptal.com/developers/gitignore/api/eclipse,java
+# Edit at https://www.toptal.com/developers/gitignore?templates=eclipse,java
+
+### Eclipse ###
+.metadata
+bin/
+tmp/
+*.tmp
+*.bak
+*.swp
+*~.nib
+local.properties
+.settings/
+.loadpath
+.recommenders
+
+# External tool builders
+.externalToolBuilders/
+
+# Locally stored "Eclipse launch configurations"
+*.launch
+
+# PyDev specific (Python IDE for Eclipse)
+*.pydevproject
+
+# CDT-specific (C/C++ Development Tooling)
+.cproject
+
+# CDT- autotools
+.autotools
+
+# Java annotation processor (APT)
+.factorypath
+
+# PDT-specific (PHP Development Tools)
+.buildpath
+
+# sbteclipse plugin
+.target
+
+# Tern plugin
+.tern-project
+
+# TeXlipse plugin
+.texlipse
+
+# STS (Spring Tool Suite)
+.springBeans
+
+# Code Recommenders
+.recommenders/
+
+# Annotation Processing
+.apt_generated/
+.apt_generated_test/
+
+# Scala IDE specific (Scala & Java development for Eclipse)
+.cache-main
+.scala_dependencies
+.worksheet
+
+# Uncomment this line if you wish to ignore the project description file.
+# Typically, this file would be tracked if it contains build/dependency configurations:
+#.project
+
+### Eclipse Patch ###
+# Spring Boot Tooling
+.sts4-cache/
+
+### Java ###
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# End of https://www.toptal.com/developers/gitignore/api/eclipse,java
+

ThreadStart/.classpath

+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-15">
+		<attributes>
+			<attribute name="module" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

ThreadStart/.project

+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>ThreadStart</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

ThreadStart/src/ThreadStarting.java

+
+public class ThreadStarting {
+
+	/*
+	 * shows different ways to create a runnable and pass it to a thread
+	 */
+	public static void main(String[] args) {
+
+		Thread[] t = new Thread[6];
+
+		t[0] = new Thread(new Runnable() {
+			@Override
+			public void run() {
+				doSomething();
+			}
+		});
+
+		t[1] = new Thread(() -> {
+			doSomething();
+		});
+
+		t[2] = new Thread(() -> doSomething());
+
+		t[3] = new Thread(ThreadStarting::doSomething);
+
+		Printer printer = new Printer();
+
+		String msg = "Hello, World";
+		t[4] = new Thread(() -> printer.doSomething(msg));
+
+		t[5] = new Thread(printer::doSomethingElse);
+
+		for (Thread a : t) {
+			if (a != null)
+				a.start();
+		}
+
+	}
+
+	static void doSomething() {
+		System.out.printf("This does something. (%s)\n", Thread.currentThread().getName());
+	}
+
+}
+
+class Printer {
+	public void doSomething(String message) {
+		System.out.printf("%s says %s\n", Thread.currentThread().getName(), message);
+	}
+
+	public void doSomethingElse() {
+		this.doSomething("Yet another method!");
+	}
+}

ThreadWaitNotify/.classpath

+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-15">
+		<attributes>
+			<attribute name="module" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

ThreadWaitNotify/.project

+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>ThreadWaitNotify</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

ThreadWaitNotify/src/Helper.java

+public class Helper {
+
+	static void log(String msg) {
+		System.out.printf("%s>\t%s\n", Thread.currentThread().getName(), msg);
+	}
+
+	static void sleep(long millis) {
+		try {
+			Thread.sleep(millis);
+		} catch (InterruptedException e) {
+			e.printStackTrace();
+		}
+	}
+}

ThreadWaitNotify/src/SyncMix.java

+public class SyncMix extends Helper {
+
+	public synchronized void synchronizedMethod() {
+		log("BeginSync");
+		sleep(1000);
+		log("EndSync");
+	}
+
+	public void unsynchronizedMethod() {
+		log("Unsynchronized");
+	}
+
+	/*
+	 * shows that synchronized blocks do not stop unsynchronized methods/blocks from
+	 * executing
+	 */
+	public static void main(String[] args) throws InterruptedException {
+
+		SyncMix mix = new SyncMix();
+
+		Thread a = new Thread(mix::synchronizedMethod);
+		Thread b = new Thread(mix::unsynchronizedMethod);
+		Thread c = new Thread(mix::synchronizedMethod);
+
+		a.start();
+		b.start();
+		c.start();
+
+		a.join();
+		b.join();
+		c.join();
+	}
+
+}
\ No newline at end of file

ThreadWaitNotify/src/WaitNotify.java

+
+public class WaitNotify extends Helper {
+
+	/*
+	 * shows how wait() and notify() interact with each other
+	 */
+	public static void main(String[] args) throws InterruptedException {
+		// lock object which we call wait and notify on
+		Object lock = new Object();
+
+		var notifier = new Thread(new Notifier(lock));
+		notifier.setName("Notifier");
+
+		var waiters = new Thread[2];
+		for (int i = 0; i < waiters.length; i++) {
+			waiters[i] = new Thread(new Waiter(lock));
+			waiters[i].setName("Waiter-" + i);
+		}
+
+		for (var waiter : waiters) {
+			waiter.start();
+		}
+
+		sleep(1000);
+
+		notifier.start();
+	}
+}
+
+
+/*
+ * calls .notify on an object.
+ */
+class Notifier extends Helper implements Runnable {
+	final Object lock;
+
+	public Notifier(Object lock) {
+		this.lock = lock;
+	}
+
+	public void run() {
+		synchronized (lock) {
+			log("Begin");
+
+			// Artificial waiting
+			sleep(1000);
+
+			log("PreNotify");
+			lock.notify();
+			log("PostNotify");
+
+			// Artificial waiting
+			sleep(1000);
+
+			log("End");
+		}
+	}
+}
+/*
+ * calls .wait on the lock object
+ */
+class Waiter extends Helper implements Runnable {
+	final Object lock;
+
+	public Waiter(Object lock) {
+		this.lock = lock;
+	}
+
+	public void run() {
+		synchronized (lock) {
+			log("Begin");
+			while (true) {
+				try {
+
+					log("PreWait");
+					lock.wait();
+					log("PostWait");
+
+					// Successfully waited
+					break;
+
+				} catch (InterruptedException e) {
+					
+					// Duh, we got interrupted
+					// Let's wait again
+
+					log("Interrupted");
+					sleep(1000);
+
+				}
+			}
+			log("End");
+		}
+	}
+}