u06-3

u06_3/Philosopher.java

@@ -0,0 +1,32 @@
+class Philosopher implements Runnable {
+
+	private Table t;
+	private int id;
+	public Philosopher(Table t, int id) {
+		this.t = t;
+		this.id = id;
+	}
+
+	public void talk() {
+		System.out.println("Philosopher " + this.id + " is talking.");
+	}
+
+	public void eat() {
+		System.out.println("Philosopher " + this.id + " is eating.");
+	}
+
+
+	public void run() {
+		talk();
+
+		try {
+			t.takeForks(this.id);
+		} catch (InterruptedException e) {
+			e.printStackTrace();
+		}
+
+		eat();
+
+		t.returnForks(this.id);
+	}
+}

u06_3/PhilosophersTest.java

@@ -0,0 +1,21 @@
+class PhilosophersTest {
+	public static void main(String[] args) {
+		int numPhilosophers = 5;
+
+		Thread[] philosophers = new Thread[numPhilosophers];
+		Table t = new Table(numPhilosophers);
+
+		for (int i = 0; i < numPhilosophers; i++) {
+			philosophers[i] = new Thread(new Philosopher(t, i));
+			philosophers[i].start();
+		}
+
+		for (int i = 0; i < numPhilosophers; i++) {
+			try {
+				philosophers[i].join();
+			} catch (InterruptedException e) {
+				e.printStackTrace();
+			}
+		}
+	}
+}

u06_3/Table.java

@@ -0,0 +1,33 @@
+import java.util.concurrent.Semaphore;
+
+class Table {
+
+	private int numForks;
+	private Semaphore[] forks;
+
+	public Table(int numForks) {
+		this.numForks = numForks;
+
+		this.forks = new Semaphore[numForks];
+		for (int i = 0; i < this.numForks; i++) {
+			this.forks[i] = new Semaphore(1);
+		}
+	}
+
+	public void takeForks(int i) throws InterruptedException {
+		int left = i;
+		int right = (i + 1) % numForks;
+		if (right > left) {
+			forks[left].acquire();
+			forks[right].acquire();
+		} else {
+			forks[right].acquire();
+			forks[left].acquire();
+		}
+	}
+
+	public void returnForks(int i) {
+		forks[i].release();
+		forks[(i + 1) % numForks].release();
+	}
+}