From 3f7dc9712cdae3acac56c6fa2c65d14ddf8580dc Mon Sep 17 00:00:00 2001
From: Karsten Jeppesen <karsten@jeppesens.com>
Date: Tue, 2 Mar 2021 16:56:04 +0100
Subject: [PATCH] GeneralMonitor - using synchronized methods and lambda
 threads

---
 GenericMonitor/.classpath              |  6 ++++
 GenericMonitor/.project                | 17 +++++++++
 GenericMonitor/src/Buffer.java         | 48 ++++++++++++++++++++++++++
 GenericMonitor/src/GenericMonitor.java | 25 ++++++++++++++
 4 files changed, 96 insertions(+)
 create mode 100644 GenericMonitor/.classpath
 create mode 100644 GenericMonitor/.project
 create mode 100644 GenericMonitor/src/Buffer.java
 create mode 100644 GenericMonitor/src/GenericMonitor.java

diff --git a/GenericMonitor/.classpath b/GenericMonitor/.classpath
new file mode 100644
index 0000000..fb50116
--- /dev/null
+++ b/GenericMonitor/.classpath
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>
diff --git a/GenericMonitor/.project b/GenericMonitor/.project
new file mode 100644
index 0000000..17c9a86
--- /dev/null
+++ b/GenericMonitor/.project
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>GenericMonitor</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>
diff --git a/GenericMonitor/src/Buffer.java b/GenericMonitor/src/Buffer.java
new file mode 100644
index 0000000..29d92fe
--- /dev/null
+++ b/GenericMonitor/src/Buffer.java
@@ -0,0 +1,48 @@
+
+// All non primary objects (int, char etc) have wait, notify, notifyAll
+// Methods "synchronized" to provide intrinsic locks
+// If a thread calling wait() method does not own the inherent lock,
+//   an error will be thrown.
+public class Buffer {
+	private int BufferSize = 4;
+	private int[] Container = {-1, -2, -3, -4};
+	private int PosR=0, PosW=0;
+	
+	public synchronized int Read() {
+		while (true) {
+			if ( PosR == PosW ) {
+				try {
+					wait();
+				} catch (InterruptedException e) {
+					// TODO Auto-generated catch block
+					e.printStackTrace();
+				}
+			} else {
+				int v=Container[ PosR ];
+				PosR = (PosR+1) % BufferSize;
+				System.out.println("Read pos " + PosR);
+				notifyAll();
+				return v;
+			}
+		}
+	}
+	
+	public synchronized void Write( int Val ) {
+		while (true) {
+			if (((PosW + 1) % BufferSize) == PosR) {
+				try {
+					wait();
+				} catch (InterruptedException e) {
+					// TODO Auto-generated catch block
+					e.printStackTrace();
+				}
+			} else {
+				Container[PosW] = Val;
+				PosW = (PosW+1) % BufferSize;
+				System.out.println("Write pos " + PosW);
+				notifyAll();
+				return;
+			}
+		}
+	}
+}
diff --git a/GenericMonitor/src/GenericMonitor.java b/GenericMonitor/src/GenericMonitor.java
new file mode 100644
index 0000000..a2a8b68
--- /dev/null
+++ b/GenericMonitor/src/GenericMonitor.java
@@ -0,0 +1,25 @@
+
+public class GenericMonitor {
+	
+	static Buffer MyBuffer = new Buffer();
+
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+
+		new Thread(() -> {
+		    System.out.println("Producer running");
+		    for ( int nn=0; nn < 20; nn++) {
+		    	MyBuffer.Write( nn );
+		    	System.out.println("Producer Wrote " + nn);
+		    }
+		}).start();
+		new Thread(() -> {
+			System.out.println("Consumer running");
+			for ( int nn=0; nn < 20; nn++ ) {
+				System.out.println("Consumer Read " + MyBuffer.Read());
+			}
+		}).start();
+		
+	}
+
+}