Merge pull request 'advanced' (#1) from develop into master

Reviewed-on: #1
Reviewed-by: Hosein Asfiaee

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

@@ -20,17 +20,18 @@ 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());
+        Resource first = (r1.getId() < r2.getId()) ? r1 : r2;
+        Resource second = (r1.getId() < r2.getId()) ? r2 : 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 " + r2.getName());
-            synchronized (r2) {
-                System.out.println("+ " + Thread.currentThread().getName() + " locked " + r2.getName());
+            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 " + r1.getName() + " and " + r2.getName());
             }
         }
@@ -40,7 +41,7 @@ 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 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
+
+    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
-                counter += 1;
+                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

@@ -3,15 +3,17 @@ package workshop.exercises;
 public class SynchronizedWorkshop {
     public static int counter = 0;
 
-    // TODO: Define a lock object to prevent race condition
+    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
-                counter += 1;
+
+                synchronized (lock) {
+                    counter += 1;
+                }
             }
             System.out.println("Increments completed by " + Thread.currentThread().getName() + ": " + i);
         }

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

@@ -21,14 +21,32 @@ public class TaylorSeries {
 
         @Override
         public void run() {
-            // TODO: Calculate the n-th term of the Taylor series for sin(x):
+            // 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.
+            int exponent = 2 * n + 1;
+
+            BigDecimal numerator = x.pow(exponent, mc);
+            if (n % 2 == 1) {
+                numerator = numerator.negate();
+            }
+
+            BigDecimal denominator = factorial(exponent);
+            BigDecimal term = numerator.divide(denominator, mc);
+
+            // Add the term to the global sum, ensuring thread-safety by
+            // synchronizing on the shared class object that guards `sum`.
+            synchronized (TaylorSeries.class) {
+                sum = sum.add(term, mc);
+            }
         }
 
-        // TODO: Implement factorial(k) using BigDecimal
+
         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));
+            }
+            return result;
         }
     }
 
@@ -39,9 +57,8 @@ public class TaylorSeries {
         sum = BigDecimal.ZERO;
         BigDecimal x = new BigDecimal("0.01");
 
-        // 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();
@@ -51,7 +68,6 @@ public class TaylorSeries {
             Thread.currentThread().interrupt();
         }
 
-        // Pre-calculated accurate value of sin(0.01) up to 1000 decimal places
         BigDecimal accurateValue = new BigDecimal("0.009999833334166664682542438269099729038964385360169151033879" +
                 "1124794097345090639159659426367929614989901525182568937606738071143914781018343679925045223748779233" +
                 "4633395662957704288475175228160558357110105077439518716860615533070998720636987509269668842490541364" +