Use command argument to choose mutex type

ta1/Main.java

@@ -5,11 +5,30 @@ class Main {
 	public static void main(String args[]){
 		System.out.println("Start thread lab");
 
-		sharedMutex = new MutexTypeD();
+		if (args.length != 1) {
+			System.err.println("ERROR : incorrect argument.");
+			showUsage();
+			return;
+		}
+
+		if (args[0].equals("D"))
+			sharedMutex = new MutexTypeD();
+		else if (args[0].equals("H"))
+			sharedMutex = new MutexTypeH();
+		else {
+			System.err.println("ERROR : unknown mutex type : " + args[0]);
+			showUsage();
+			return;
+		}
 
 		runExperiment();
 	}
 
+	private static void showUsage() {
+		System.out.println("Usage : java Main <mutex_type>");
+		System.out.println("Where <mutex_type> is one of D|A|H|P");
+	}
+
 	private static void runExperiment() {
 		Task t0 = new Task("T0", 0, sharedMutex);
 		Task t1 = new Task("T1", 1, sharedMutex);

ta1/MutexTypeH.java

@@ -0,0 +1,31 @@
+
+class MutexTypeH extends Mutex {
+
+	private volatile int turn;
+	private volatile boolean[] flag;
+	
+	MutexTypeH() {
+		turn = 0;
+
+		flag = new boolean[2];
+		flag[0] = flag[1] = false;
+	}
+
+	public void p(int id) {
+		int other = 1 - id;
+		flag[id] = true;
+
+		while (turn == other) {
+			while (flag[other]) Thread.yield();
+			turn = id;
+		}
+	}
+
+	public void v(int id) {
+		flag[id] = false;
+	}
+
+	public String toString() {
+		return "H";
+	}
+}