From 5937fdaba2b328d0b3759a6941ecf5d4648ca26b Mon Sep 17 00:00:00 2001 From: mohammadreza Date: Tue, 9 Jun 2026 18:33:57 +0330 Subject: [PATCH] implement all TODO tasks --- .../exercises/DeadlockPreventionWorkshop.java | 35 +++++++++++------ .../java/workshop/exercises/LockWorkshop.java | 13 +++++-- .../exercises/SynchronizedWorkshop.java | 8 ++-- .../java/workshop/exercises/TaylorSeries.java | 38 +++++++++++++++---- 4 files changed, 70 insertions(+), 24 deletions(-) diff --git a/src/main/java/workshop/exercises/DeadlockPreventionWorkshop.java b/src/main/java/workshop/exercises/DeadlockPreventionWorkshop.java index 91ba6a8..77aa717 100644 --- a/src/main/java/workshop/exercises/DeadlockPreventionWorkshop.java +++ b/src/main/java/workshop/exercises/DeadlockPreventionWorkshop.java @@ -20,18 +20,31 @@ 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, second; System.out.println(Thread.currentThread().getName() + " is attempting to lock " + r1.getName()); - synchronized (r1) { - System.out.println("+ " + Thread.currentThread().getName() + " locked " + r1.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()); + + if (r1.getId() < r2.getId()) { + first = r1; + second = r2; + } else { + first = r2; + second = r1; + } + + synchronized (first) { + System.out.println("+ " + Thread.currentThread().getName() + " locked " + first.getName()); + try { + Thread.sleep(100); + } + catch (InterruptedException e) { + Thread.currentThread().interrupt(); + return; + } + + 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..a5a02d6 100644 --- a/src/main/java/workshop/exercises/LockWorkshop.java +++ b/src/main/java/workshop/exercises/LockWorkshop.java @@ -6,15 +6,22 @@ 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 ReentrantLock 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); } diff --git a/src/main/java/workshop/exercises/SynchronizedWorkshop.java b/src/main/java/workshop/exercises/SynchronizedWorkshop.java index 9259d8e..4eaf01e 100644 --- a/src/main/java/workshop/exercises/SynchronizedWorkshop.java +++ b/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); } diff --git a/src/main/java/workshop/exercises/TaylorSeries.java b/src/main/java/workshop/exercises/TaylorSeries.java index d63a18e..8ae3ad7 100644 --- a/src/main/java/workshop/exercises/TaylorSeries.java +++ b/src/main/java/workshop/exercises/TaylorSeries.java @@ -8,7 +8,9 @@ import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; public class TaylorSeries { - + + private static final Object lock = new Object(); + public static class CalculateSin implements Runnable { private final MathContext mc = new MathContext(1000); private final BigDecimal x; @@ -21,14 +23,35 @@ 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. + BigDecimal numerator = x.pow(2*n+1, mc); + + if (n % 2 != 0) { + + numerator = numerator.negate(); + } + + BigDecimal denominator = factorial(2*n+1); + + BigDecimal term = numerator.divide(denominator, mc); + + synchronized (lock) { + sum = sum.add(term, mc); + } } - // TODO: Implement factorial(k) using BigDecimal private BigDecimal factorial(int k) { - return BigDecimal.ZERO; + if (k < 0) { + throw new IllegalArgumentException("k most be non-negative"); + } + + BigDecimal result = BigDecimal.ONE; + + for (int i = 2; i <=k; i++) { + + result = result.multiply(BigDecimal.valueOf(i)); + } + + return result; } } @@ -41,7 +64,8 @@ public class TaylorSeries { // Submit tasks to calculate terms for (int i = 0; i < 100; i++) { - // TODO: Submit task to the thread pool + + threadPool.execute(new CalculateSin(x, i)); } threadPool.shutdown();