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target/
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.idea/
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*.iml
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*.iws
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*.ipr
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.settings/
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.classpath
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.project
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.DS_Store
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# Advanced Multithreading Workshop
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This project contains the workshop materials for the Advanced Programming multithreading session. It has been migrated from Gradle to Maven and structured for clear delivery.
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## Project Structure
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- `src/main/java/workshop/exercises/`: Unsolved skeleton files with clear `TODO` markers. These are the templates to distribute to students and use during live coding.
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- `src/main/java/workshop/solutions/`: Fully implemented reference solutions for grading and internal testing.
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## Exercises Covered
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1. **`LockWorkshop`**: Resolving race conditions on a shared mutable counter using explicit `ReentrantLock` coordination.
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2. **`SynchronizedWorkshop`**: Resolving race conditions on a shared mutable counter using intrinsic Java monitors (`synchronized` block).
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3. **`DeadlockPreventionWorkshop`**: Resolving a classic thread circular wait condition by enforcing global lock ordering based on unique Resource IDs.
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4. **`TaylorSeries`**: Implementing high-precision math with `BigDecimal` and calculating the Taylor series for $\sin(x)$ using a thread pool (`ExecutorService`).
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## Requirements
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- Java 17 or higher
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- Apache Maven 3.6+
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## How to Build and Run
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To compile the project:
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```bash
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mvn clean compile
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```
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To execute any of the workshop main classes (for example, the Lock Workshop solution):
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```bash
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mvn exec:java -Dexec.mainClass="workshop.solutions.LockWorkshopSolution"
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```
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>com.university.advancedprogramming</groupId>
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<artifactId>multithreading-workshop</artifactId>
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<version>1.0-SNAPSHOT</version>
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<properties>
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<maven.compiler.source>17</maven.compiler.source>
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<maven.compiler.target>17</maven.compiler.target>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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</properties>
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<dependencies>
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<dependency>
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<groupId>org.junit.jupiter</groupId>
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<artifactId>junit-jupiter-api</artifactId>
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<version>5.10.0</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.junit.jupiter</groupId>
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<artifactId>junit-jupiter-engine</artifactId>
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<version>5.10.0</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>3.11.0</version>
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</plugin>
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</plugins>
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</build>
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</project>
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package workshop.exercises;
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public class DeadlockPreventionWorkshop {
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public static class Resource {
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private final int id;
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private final String name;
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public Resource(int id, String name) {
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this.id = id;
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this.name = name;
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}
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public int getId() {
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return id;
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}
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public String getName() {
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return name;
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}
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}
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public static void useResources(Resource r1, Resource r2) {
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// TODO: Prevent deadlock by enforcing a consistent lock acquisition order
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// Hint: Compare resource IDs and always synchronize on the resource with the smaller ID first.
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System.out.println(Thread.currentThread().getName() + " is attempting to lock " + r1.getName());
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synchronized (r1) {
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System.out.println("+ " + Thread.currentThread().getName() + " locked " + r1.getName());
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try { Thread.sleep(100); } catch (InterruptedException ignored) {}
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System.out.println(Thread.currentThread().getName() + " is attempting to lock " + r2.getName());
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synchronized (r2) {
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System.out.println("+ " + Thread.currentThread().getName() + " locked " + r2.getName());
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System.out.println(Thread.currentThread().getName() + " using " + r1.getName() + " and " + r2.getName());
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}
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}
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}
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public static void main(String[] args) {
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Resource resA = new Resource(1, "ResourceA");
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Resource resB = new Resource(2, "ResourceB");
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// Thread 1 locks A then B; Thread 2 locks B then A (causing deadlock if unordered)
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Thread t1 = new Thread(() -> useResources(resA, resB), "Thread-1");
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Thread t2 = new Thread(() -> useResources(resB, resA), "Thread-2");
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t1.start();
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t2.start();
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}
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}
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package workshop.exercises;
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import java.util.concurrent.locks.Lock;
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import java.util.concurrent.locks.ReentrantLock;
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public class LockWorkshop {
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public static int counter = 0;
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// TODO: Create a ReentrantLock instance to protect the critical section
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public static class MyRunnable implements Runnable {
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@Override
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public void run() {
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int i;
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for (i = 0; i < 1_000_000; i++) {
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// TODO: Acquire the lock, increment the counter, and release the lock safely in a finally block
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counter += 1;
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}
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System.out.println("Increments completed by " + Thread.currentThread().getName() + ": " + i);
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}
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}
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public static void main(String[] args) throws InterruptedException {
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counter = 0;
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Thread thread1 = new Thread(new MyRunnable(), "Thread-1");
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Thread thread2 = new Thread(new MyRunnable(), "Thread-2");
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thread1.start();
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thread2.start();
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thread1.join();
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thread2.join();
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System.out.println("Final counter value (expected 2000000): " + counter);
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}
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}
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package workshop.exercises;
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public class SynchronizedWorkshop {
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public static int counter = 0;
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// TODO: Define a lock object to prevent race condition
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public static class MyRunnable implements Runnable {
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@Override
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public void run() {
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int i;
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for (i = 0; i < 1_000_000; i++) {
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// TODO: Use a synchronized block to protect the counter increment
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counter += 1;
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}
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System.out.println("Increments completed by " + Thread.currentThread().getName() + ": " + i);
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}
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}
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public static void main(String[] args) throws InterruptedException {
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counter = 0;
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Thread thread1 = new Thread(new MyRunnable(), "Thread-1");
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Thread thread2 = new Thread(new MyRunnable(), "Thread-2");
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thread1.start();
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thread2.start();
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thread1.join();
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thread2.join();
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System.out.println("Final counter value (expected 2000000): " + counter);
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}
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}
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package workshop.exercises;
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import java.math.BigDecimal;
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import java.math.MathContext;
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import java.math.RoundingMode;
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import java.util.concurrent.ExecutorService;
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import java.util.concurrent.Executors;
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import java.util.concurrent.TimeUnit;
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public class TaylorSeries {
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public static class CalculateSin implements Runnable {
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private final MathContext mc = new MathContext(1000);
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private final BigDecimal x;
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private final int n;
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public CalculateSin(BigDecimal x, int n) {
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this.x = x;
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this.n = n;
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}
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@Override
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public void run() {
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// TODO: Calculate the n-th term of the Taylor series for sin(x):
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// term = (-1)^n * (x^(2n+1)) / (2n+1)!
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// Add the term to the global sum ensuring thread-safety.
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}
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// TODO: Implement factorial(k) using BigDecimal
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private BigDecimal factorial(int k) {
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return BigDecimal.ZERO;
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}
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}
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public static BigDecimal sum = BigDecimal.ZERO;
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public static void main(String[] args) {
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ExecutorService threadPool = Executors.newFixedThreadPool(4);
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sum = BigDecimal.ZERO;
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BigDecimal x = new BigDecimal("0.01");
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// Submit tasks to calculate terms
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for (int i = 0; i < 100; i++) {
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// TODO: Submit task to the thread pool
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}
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threadPool.shutdown();
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try {
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threadPool.awaitTermination(10, TimeUnit.SECONDS);
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} catch (InterruptedException e) {
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Thread.currentThread().interrupt();
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}
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// Pre-calculated accurate value of sin(0.01) up to 1000 decimal places
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BigDecimal accurateValue = new BigDecimal("0.009999833334166664682542438269099729038964385360169151033879" +
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"1124794097345090639159659426367929614989901525182568937606738071143914781018343679925045223748779233" +
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"4633395662957704288475175228160558357110105077439518716860615533070998720636987509269668842490541364" +
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"2046237535076816415219593915753970609625155007149734343650140126010756472960507873872984042987441343" +
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"4632784947709943715670321717675280271359744354619523360203501121465199963741173489051927920551271878" +
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"0890799396861427770050764919858890678677220571952090318596147460309593993397336341626522171452145068" +
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"2733933417711179372733354590095099959888961964291389175600643442999116373725594047366187408263088683" +
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"4976343405988894064532908768068263525544004211332459809773301487980907370431155859574851192235000645" +
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"6064003773432638837702651724406011257895842835907410397326351149391214249645075873929695397792073094" +
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"1188402364506858174852606021099282767046225114299907364917050686481947141812831031312882254660611456" +
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"524573907422800164140884130285721050703575");
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sum = sum.setScale(1000, RoundingMode.HALF_DOWN);
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accurateValue = accurateValue.setScale(1000, RoundingMode.HALF_DOWN);
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System.out.println("sin(0.01) up to 1000 decimal places:");
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System.out.println("Calculated Value: " + sum.toPlainString());
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System.out.println("Accurate Value: " + accurateValue.toPlainString());
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System.out.println("Difference: " + accurateValue.subtract(sum).abs().toPlainString());
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}
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}
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