exercises : Solve multithreading

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

@@ -20,18 +20,19 @@ public class DeadlockPreventionWorkshop {
     }
 
     public static void useResources(Resource r1, Resource r2) {
-        // TODO: Prevent deadlock by enforcing a consistent lock acquisition order
+        // تشخیص اینکه کدام منبع ID کوچکتر و کدام بزرگتر دارد
-        // 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() + " is attempting to lock " + firstLock.getName());
-            System.out.println("+ " + Thread.currentThread().getName() + " locked " + r1.getName());
+        synchronized (firstLock) {
+            System.out.println("  " + Thread.currentThread().getName() + " locked " + firstLock.getName());
             try { Thread.sleep(100); } catch (InterruptedException ignored) {}
-            
+
-            System.out.println(Thread.currentThread().getName() + " is attempting to lock " + r2.getName());
+            System.out.println(Thread.currentThread().getName() + " is attempting to lock " + secondLock.getName());
-            synchronized (r2) {
+            synchronized (secondLock) {
-                System.out.println("+ " + Thread.currentThread().getName() + " locked " + r2.getName());
+                System.out.println("  " + Thread.currentThread().getName() + " locked " + secondLock.getName());
-                System.out.println(Thread.currentThread().getName() + " using " + r1.getName() + " and " + r2.getName());
+                System.out.println(Thread.currentThread().getName() + " is using " + firstLock.getName() + " and " + secondLock.getName());
             }
         }
     }

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

@@ -5,16 +5,20 @@ 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 java.util.concurrent.locks.ReentrantLock lock = new java.util.concurrent.locks.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();
-                counter += 1;
+                try {
+                    counter += 1;
+                } finally {
+                    lock.unlock();
+                }
             }
             System.out.println("Increments completed by " + Thread.currentThread().getName() + ": " + i);
         }

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

@@ -2,16 +2,17 @@ package workshop.exercises;
 
 public class SynchronizedWorkshop {
     public static int counter = 0;
-    
+
-    // TODO: Define a lock object to prevent race condition
+    private static final Object lockObject = 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
+                synchronized (lockObject) {
-                counter += 1;
+                    counter += 1;
+                }
             }
             System.out.println("Increments completed by " + Thread.currentThread().getName() + ": " + i);
         }

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

@@ -8,7 +8,7 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 
 public class TaylorSeries {
-    
+
     public static class CalculateSin implements Runnable {
         private final MathContext mc = new MathContext(1000);
         private final BigDecimal x;
@@ -21,14 +21,32 @@ public class TaylorSeries {
 
         @Override
         public void run() {
-            // TODO: Calculate the n-th term of the Taylor series for sin(x):
+            // ۱. محاسبه صورت کسر: (-1)^n * x^(2n+1)
-            // term = (-1)^n * (x^(2n+1)) / (2n+1)!
+            int exponent = 2 * n + 1;
-            // Add the term to the global sum ensuring thread-safety.
+            BigDecimal numerator = x.pow(exponent, mc);
+            if (n % 2 != 0) {
+                numerator = numerator.negate();
+            }
+
+            // ۲. محاسبه مخرج کسر: (2n+1)!
+            BigDecimal denominator = factorial(exponent);
+
+            // ۳. تقسیم صورت بر مخرج
+            BigDecimal term = numerator.divide(denominator, mc);
+
+            // ۴. جمع زدن ایمن با متغیر جهانی sum
+            synchronized (TaylorSeries.class) {
+                sum = sum.add(term, mc);
+            }
         }
 
-        // TODO: Implement factorial(k) using BigDecimal
+        // پیاده‌سازی متد فاکتوریل
         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;
         }
     }
 
@@ -41,7 +59,8 @@ public class TaylorSeries {
 
         // Submit tasks to calculate terms
         for (int i = 0; i < 100; i++) {
-            // TODO: Submit task to the thread pool
+            // جایگذاری TODO سوم: ارسال تسک به ترد پول
+            threadPool.submit(new CalculateSin(x, i));
         }
 
         threadPool.shutdown();