Merge pull request 'complete advanced multithreading exercises' (#1) from develope into master

Reviewed-on: #1

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

@@ -22,7 +22,9 @@ 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.
-        
+        Resource firstLock = r1.getId() < r2.getId() ? r1 : r2;
+        Resource secondLock = r1.getId() < r2.getId() ? r2 : r1;
+
         System.out.println(Thread.currentThread().getName() + " is attempting to lock " + r1.getName());
         synchronized (r1) {
             System.out.println("+ " + Thread.currentThread().getName() + " locked " + r1.getName());

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

@@ -7,6 +7,7 @@ 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
@@ -14,7 +15,13 @@ public class LockWorkshop {
             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

@@ -4,6 +4,7 @@ public class SynchronizedWorkshop {
     public static int counter = 0;
     
     // TODO: Define a lock object to prevent race condition
+    private static final Object lockObject = new Object();
 
     public static class MyRunnable implements Runnable {
         @Override
@@ -11,7 +12,9 @@ public class SynchronizedWorkshop {
             int i;
             for (i = 0; i < 1_000_000; i++) {
                 // TODO: Use a synchronized block to protect the counter increment
-                counter += 1;
+                synchronized (lockObject){
+                    counter += 1;
+                }
             }
             System.out.println("Increments completed by " + Thread.currentThread().getName() + ": " + i);
         }

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

@@ -24,11 +24,27 @@ public class TaylorSeries {
             // 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.
+            int power = 2 * n + 1;
+            BigDecimal num = x.pow(power, mc);
+            BigDecimal den = factorial(power);
+            BigDecimal term = num.divide(den, mc);
+
+            if (n % 2 != 0){
+                term = term.negate();
+            }
+
+            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(new BigDecimal(i), mc);
+            }
+            return result;
         }
     }
 
@@ -42,6 +58,7 @@ 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();