2. Monitors

Concurrency

MonitorCase1/src/Buffer.java

@@ -0,0 +1,28 @@
+
+public class Buffer {
+	private char[] buffer;
+	private int count = 0, in = 0, out = 0;
+
+	Buffer(int size) {
+		buffer = new char[size];
+	}
+
+	public synchronized void Put(char c) {
+		while (count == buffer.length)
+			;
+		System.out.println("Producing " + c + " ...");
+		buffer[in] = c;
+		in = (in + 1) % buffer.length;
+		count++;
+	}
+
+	public synchronized char Get() {
+		while (count == 0)
+			;
+		char c = buffer[out];
+		out = (out + 1) % buffer.length;
+		count--;
+		System.out.println("Consuming " + c + " ...");
+		return c;
+	}
+}

MonitorCase1/src/PC.java

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+/*
+ *  Run this code.
+ *  1: What happens ?
+ *  2: Why does it happen ?
+ *  
+ *  Code courtesy of www.csc.villanova.edu/~mdamian/threads/javamonitors.html
+ */
+public class PC {
+
+	public static void main(String[] args) {
+		Buffer b = new Buffer(4);
+		Producer p = new Producer(b);
+		Consumer c = new Consumer(b);
+
+		p.start();
+		c.start();
+	}
+
+}

MonitorCase1/src/ProCon.java

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+class Producer extends Thread {
+	private Buffer buffer;
+
+	Producer(Buffer b) {
+		buffer = b;
+	}
+
+	public void run() {
+		for (int i = 0; i < 10; i++) {
+			buffer.Put((char) ('A' + i % 26));
+		}
+	}
+}
+
+class Consumer extends Thread {
+	private Buffer buffer;
+
+	Consumer(Buffer b) {
+		buffer = b;
+	}
+
+	public void run() {
+		for (int i = 0; i < 10; i++) {
+			buffer.Get();
+		}
+	}
+}