Workshop-8

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());
             }
         }

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

@@ -6,15 +6,19 @@ import java.util.concurrent.locks.ReentrantLock;
 public class LockWorkshop {
     public static int counter = 0;
     
-    // TODO: Create a ReentrantLock instance to protect the critical section
+    public 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 +3,16 @@ 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

@@ -8,6 +8,8 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 
 public class TaylorSeries {
+    public static BigDecimal sum = BigDecimal.ZERO;
+    private static final Object sumLock = new Object();
     
     public static class CalculateSin implements Runnable {
         private final MathContext mc = new MathContext(1000);
@@ -19,29 +21,44 @@ public class TaylorSeries {
             this.n = n;
         }
 
+        private static void accumulate(BigDecimal term) {
+            synchronized (sumLock) {
+                sum = sum.add(term);
+            }
+        }
+
         @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.
+            int exponent = (2 * n) + 1;
+
+            BigDecimal termNumerator = x.pow(exponent, mc);
+            BigDecimal termDominator = factorial(exponent);
+
+            BigDecimal termValue = termNumerator.divide(termDominator, mc);
+
+            if (n % 2 != 0) {
+                termValue = termValue.negate();
+            }
+
+            accumulate(termValue);
         }
 
-        // TODO: Implement factorial(k) using BigDecimal
         private BigDecimal factorial(int k) {
-            return BigDecimal.ZERO;
+            BigDecimal result = BigDecimal.ONE;
+            for (int i = 1; i <= k; i++) {
+                result = result.multiply(BigDecimal.valueOf(i), mc);
+            }
+            return result;
         }
     }
 
-    public static BigDecimal sum = BigDecimal.ZERO;
-
     public static void main(String[] args) {
         ExecutorService threadPool = Executors.newFixedThreadPool(4);
         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
+        for (int i = 0; i < 126; i++) {
+            threadPool.execute(new CalculateSin(x, i));
         }
 
         threadPool.shutdown();