From d236a595425fe57137ffce52ef63bcc3c5d245f3 Mon Sep 17 00:00:00 2001 From: Rezak Date: Wed, 3 Jun 2026 14:49:38 +0330 Subject: [PATCH] complete --- .../exercises/DeadlockPreventionWorkshop.java | 18 ++++++------ .../java/workshop/exercises/LockWorkshop.java | 11 +++++--- .../exercises/SynchronizedWorkshop.java | 8 +++--- .../java/workshop/exercises/TaylorSeries.java | 28 ++++++++++++------- 4 files changed, 38 insertions(+), 27 deletions(-) diff --git a/src/main/java/workshop/exercises/DeadlockPreventionWorkshop.java b/src/main/java/workshop/exercises/DeadlockPreventionWorkshop.java index 91ba6a8..a9c8498 100644 --- a/src/main/java/workshop/exercises/DeadlockPreventionWorkshop.java +++ b/src/main/java/workshop/exercises/DeadlockPreventionWorkshop.java @@ -20,18 +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. + 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 " + r1.getName()); - synchronized (r1) { - System.out.println("+ " + Thread.currentThread().getName() + " locked " + r1.getName()); + 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() + " using " + r1.getName() + " and " + 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 " + first.getName() + " and " + second.getName()); } } } diff --git a/src/main/java/workshop/exercises/LockWorkshop.java b/src/main/java/workshop/exercises/LockWorkshop.java index ec24ecf..59eeb31 100644 --- a/src/main/java/workshop/exercises/LockWorkshop.java +++ b/src/main/java/workshop/exercises/LockWorkshop.java @@ -5,16 +5,19 @@ import java.util.concurrent.locks.ReentrantLock; public class LockWorkshop { public static int counter = 0; + private static final Lock lock = new ReentrantLock(); - // TODO: Create a ReentrantLock instance to protect the critical section - 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); } diff --git a/src/main/java/workshop/exercises/SynchronizedWorkshop.java b/src/main/java/workshop/exercises/SynchronizedWorkshop.java index 9259d8e..32a5d79 100644 --- a/src/main/java/workshop/exercises/SynchronizedWorkshop.java +++ b/src/main/java/workshop/exercises/SynchronizedWorkshop.java @@ -2,16 +2,16 @@ package workshop.exercises; public class SynchronizedWorkshop { public static int counter = 0; + public static final Object lock = new Object(); - // TODO: Define a lock object to prevent race condition - 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); } diff --git a/src/main/java/workshop/exercises/TaylorSeries.java b/src/main/java/workshop/exercises/TaylorSeries.java index d63a18e..aeaa1f8 100644 --- a/src/main/java/workshop/exercises/TaylorSeries.java +++ b/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 lock = new Object(); public static class CalculateSin implements Runnable { private final MathContext mc = new MathContext(1000); @@ -21,27 +23,34 @@ 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. + int p = 2 * n + 1; + BigDecimal sign = (n % 2 == 0) ? BigDecimal.ONE : new BigDecimal("-1"); + BigDecimal num = x.pow(p, mc); + BigDecimal den = factorial(p); + BigDecimal term = sign.multiply(num, mc).divide(den, mc); + + synchronized (lock) { + sum = sum.add(term, mc); + } } - // TODO: Implement factorial(k) using BigDecimal + private BigDecimal factorial(int k) { - return BigDecimal.ZERO; + BigDecimal f = BigDecimal.ONE; + for (int i = 2; i <= k; i++) { + f = f.multiply(BigDecimal.valueOf(i)); + } + return f; } } - 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 + threadPool.submit(new CalculateSin(x, i)); } threadPool.shutdown(); @@ -51,7 +60,6 @@ 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" +