implementation of WS-08 is complete

src/main/java/workshop/exercises/DeadlockPreventionWorkshop.java

@@ -20,18 +20,38 @@ public class DeadlockPreventionWorkshop {
     }
 
     public static void useResources(Resource r1, Resource r2) {
-        // TODO: Prevent deadlock by enforcing a consistent lock acquisition order
-        // Hint: Compare resource IDs and always synchronize on the resource with the smaller ID first.
 
-        System.out.println(Thread.currentThread().getName() + " is attempting to lock " + r1.getName());
-        synchronized (r1) {
-            System.out.println("+ " + Thread.currentThread().getName() + " locked " + r1.getName());
-            try { Thread.sleep(100); } catch (InterruptedException ignored) {}
+        // Always lock resources in ascending order of ID
+        Resource first = r1;
+        Resource second = r2;
 
-            System.out.println(Thread.currentThread().getName() + " is attempting to lock " + r2.getName());
-            synchronized (r2) {
-                System.out.println("+ " + Thread.currentThread().getName() + " locked " + r2.getName());
-                System.out.println(Thread.currentThread().getName() + " using " + r1.getName() + " and " + r2.getName());
+        if (r1.getId() > r2.getId()) {
+            first = r2;
+            second = r1;
+        }
+
+        System.out.println(Thread.currentThread().getName()
+                + " is attempting to lock " + first.getName());
+
+        synchronized (first) {
+            System.out.println("+ " + Thread.currentThread().getName()
+                    + " locked " + first.getName());
+
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException ignored) {
+            }
+
+            System.out.println(Thread.currentThread().getName()
+                    + " is attempting to lock " + second.getName());
+
+            synchronized (second) {
+                System.out.println("+ " + Thread.currentThread().getName()
+                        + " locked " + second.getName());
+
+                System.out.println(Thread.currentThread().getName()
+                        + " using " + first.getName()
+                        + " and " + second.getName());
             }
         }
     }
@@ -40,7 +60,8 @@ public class DeadlockPreventionWorkshop {
         Resource resA = new Resource(1, "ResourceA");
         Resource resB = new Resource(2, "ResourceB");
 
-        // Thread 1 locks A then B; Thread 2 locks B then A (causing deadlock if unordered)
+        // Thread 1 requests A then B
+        // Thread 2 requests B then A
         Thread t1 = new Thread(() -> useResources(resA, resB), "Thread-1");
         Thread t2 = new Thread(() -> useResources(resB, resA), "Thread-2");
 

src/main/java/workshop/exercises/LockWorkshop.java

@@ -6,15 +6,20 @@ import java.util.concurrent.locks.ReentrantLock;
 public class LockWorkshop {
     public static int counter = 0;
 
-    // TODO: Create a ReentrantLock instance to protect the critical section
+    // Lock protecting the shared counter
+    private static final Lock lock = new ReentrantLock();
 
     public static class MyRunnable implements Runnable {
         @Override
         public void run() {
             int i;
             for (i = 0; i < 1_000_000; i++) {
-                // TODO: Acquire the lock, increment the counter, and release the lock safely in a finally block
+                lock.lock();
+                try {
                     counter += 1;
+                } finally {
+                    lock.unlock();
+                }
             }
             System.out.println("Increments completed by " + Thread.currentThread().getName() + ": " + i);
         }

src/main/java/workshop/exercises/SynchronizedWorkshop.java

@@ -3,16 +3,19 @@ package workshop.exercises;
 public class SynchronizedWorkshop {
     public static int counter = 0;
 
-    // TODO: Define a lock object to prevent race condition
+    // Lock object used for synchronization
+    private static final Object lock = new Object();
 
     public static class MyRunnable implements Runnable {
         @Override
         public void run() {
             int i;
             for (i = 0; i < 1_000_000; i++) {
-                // TODO: Use a synchronized block to protect the counter increment
+                // Protect the shared counter
+                synchronized (lock) {
                     counter += 1;
                 }
+            }
             System.out.println("Increments completed by " + Thread.currentThread().getName() + ": " + i);
         }
     }

src/main/java/workshop/exercises/TaylorSeries.java

@@ -21,14 +21,34 @@ public class TaylorSeries {
 
         @Override
         public void run() {
-            // TODO: Calculate the n-th term of the Taylor series for sin(x):
-            // term = (-1)^n * (x^(2n+1)) / (2n+1)!
-            // Add the term to the global sum ensuring thread-safety.
+            // term = (-1)^n * x^(2n+1) / (2n+1)!
+
+            int exponent = 2 * n + 1;
+
+            BigDecimal numerator = x.pow(exponent, mc);
+            BigDecimal denominator = factorial(exponent);
+
+            BigDecimal term = numerator.divide(denominator, mc);
+
+            if (n % 2 == 1) {
+                term = term.negate();
             }
 
-        // TODO: Implement factorial(k) using BigDecimal
+            // Thread-safe update of the global sum
+            synchronized (TaylorSeries.class) {
+                sum = sum.add(term, mc);
+            }
+        }
+
+        // Computes k!
         private BigDecimal factorial(int k) {
-            return BigDecimal.ZERO;
+            BigDecimal result = BigDecimal.ONE;
+
+            for (int i = 2; i <= k; i++) {
+                result = result.multiply(BigDecimal.valueOf(i), mc);
+            }
+
+            return result;
         }
     }
 
@@ -41,7 +61,7 @@ public class TaylorSeries {
 
         // Submit tasks to calculate terms
         for (int i = 0; i < 100; i++) {
-            // TODO: Submit task to the thread pool
+            threadPool.submit(new CalculateSin(x, i));
         }
 
         threadPool.shutdown();