import java.io.*; import java.nio.file.*; import java.util.*; import java.util.concurrent.*; /** * IT6003 - Advanced Java Programming * Practice Exercises: Threads and I/O * * Instructions: * - Implement each method/class where you see the // TODO comment. * - Do NOT change the method signatures. * - Run main() to test your implementations. * - Some exercises create files in a "temp" folder inside the working directory. */ public class ExercisesThreadsIO { // ────────────────────────────────────────────── // Exercise 1: Thread Subclass – Print 1 to 10 // ────────────────────────────────────────────── /** * Create a class NumberThread that extends Thread. * In its run() method, print numbers 1 through 10 * (each on a new line, prefixed with the thread name). * * Example output line: NumberThread: 1 */ static class NumberThread extends Thread { // TODO: Override the run() method to print numbers 1-10. // Use getName() to prefix each line. public NumberThread() { super("NumberThread"); } @Override public void run() { // TODO: Print numbers 1 to 10 } } // ────────────────────────────────────────────── // Exercise 2: Runnable – Print Even Numbers 2-20 // ────────────────────────────────────────────── /** * Create a Runnable that prints even numbers from 2 to 20. * * @return a Runnable whose run() prints even numbers 2..20 */ public static Runnable createEvenPrinter() { // TODO: Return a Runnable (lambda or anonymous class) that // prints even numbers from 2 to 20, each on a new line. return null; } // ────────────────────────────────────────────── // Exercise 3: Thread.join() – Sequential Execution // ────────────────────────────────────────────── /** * Create two threads: * - Thread A prints "A1" through "A5" * - Thread B prints "B1" through "B5" * Use join() so that Thread A completes entirely before Thread B starts. */ public static void runSequentially() throws InterruptedException { // TODO: Create Thread A, start it, call join(). // Then create Thread B, start it, call join(). } // ────────────────────────────────────────────── // Exercise 4: Synchronized Counter // ────────────────────────────────────────────── /** * Implement a thread-safe counter with increment(), decrement(), * and getCount() methods. All methods must be synchronized. */ static class SynchronizedCounter { private int count = 0; // TODO: Implement synchronized void increment() public synchronized void increment() { // TODO } // TODO: Implement synchronized void decrement() public synchronized void decrement() { // TODO } // TODO: Implement synchronized int getCount() public synchronized int getCount() { // TODO return 0; } } // ────────────────────────────────────────────── // Exercise 5: Write to File (BufferedWriter) // ────────────────────────────────────────────── /** * Write the given lines to a file using BufferedWriter with * try-with-resources. Each string should be on its own line. * * @param filePath the path of the file to create/overwrite * @param lines the lines to write */ public static void writeToFile(String filePath, List lines) throws IOException { // TODO: Use try-with-resources with a BufferedWriter (via FileWriter) // to write each line followed by newLine(). } // ────────────────────────────────────────────── // Exercise 6: Read File Line by Line (BufferedReader) // ────────────────────────────────────────────── /** * Read a text file line by line using BufferedReader and return * all lines as a List. * * @param filePath the path of the file to read * @return list of lines from the file */ public static List readFromFile(String filePath) throws IOException { // TODO: Use try-with-resources with a BufferedReader (via FileReader) // to read all lines into a list and return it. return null; } // ────────────────────────────────────────────── // Exercise 7: Count Lines, Words, Characters // ────────────────────────────────────────────── /** * Count the number of lines, words, and characters in a file * using Files.lines(). * * @param filePath the path of the file * @return an int array: [lineCount, wordCount, charCount] */ public static int[] countFileStats(String filePath) throws IOException { // TODO: Use Files.lines(Path) to stream lines. // Count lines, split each line into words to count words, // and sum line lengths (including newline) for characters. // Return {lineCount, wordCount, charCount}. return null; } // ────────────────────────────────────────────── // Exercise 8: Copy File Using NIO // ────────────────────────────────────────────── /** * Copy the contents of the source file to the destination file * using java.nio.file.Files.copy(). Overwrite if destination exists. * * @param source path of the source file * @param dest path of the destination file */ public static void copyFile(String source, String dest) throws IOException { // TODO: Use Files.copy(Path, Path, StandardCopyOption.REPLACE_EXISTING). } // ────────────────────────────────────────────── // Exercise 9: Serialize and Deserialize a Student // ────────────────────────────────────────────── /** * A simple Student class that implements Serializable. */ static class Student implements Serializable { private static final long serialVersionUID = 1L; String name; String regNo; double gpa; Student(String name, String regNo, double gpa) { this.name = name; this.regNo = regNo; this.gpa = gpa; } @Override public String toString() { return name + " (" + regNo + ", GPA: " + gpa + ")"; } } /** * Serialize the given Student object to a file. * * @param student the student to serialize * @param filePath the file to write to */ public static void serializeStudent(Student student, String filePath) throws IOException { // TODO: Use ObjectOutputStream wrapping FileOutputStream in // try-with-resources. Call writeObject(student). } /** * Deserialize a Student object from a file. * * @param filePath the file to read from * @return the deserialized Student */ public static Student deserializeStudent(String filePath) throws IOException, ClassNotFoundException { // TODO: Use ObjectInputStream wrapping FileInputStream in // try-with-resources. Call readObject() and cast to Student. return null; } // ────────────────────────────────────────────── // Exercise 10: ExecutorService with Callable // ────────────────────────────────────────────── /** * Use an ExecutorService with a fixed thread pool of 3 threads to * execute 5 Callable tasks. Each task should: * - Sleep for a random time between 100-500ms * - Return "Task completed by " * * Collect and return all results. * * @return list of result strings from all 5 tasks */ public static List runCallableTasks() throws InterruptedException, ExecutionException { // TODO: Create ExecutorService with Executors.newFixedThreadPool(3). // Submit 5 Callable tasks that sleep and return a message. // Collect Future results, call get() on each, and return. // Shut down the executor. return null; } // ────────────────────────────────────────────── // Main – test your implementations here // ────────────────────────────────────────────── public static void main(String[] args) throws Exception { // Create a temp directory for file exercises String tempDir = "temp_exercises"; Files.createDirectories(Paths.get(tempDir)); System.out.println("=== Exercise 1: Thread Subclass ==="); NumberThread nt = new NumberThread(); nt.start(); nt.join(); // Expected: NumberThread: 1 ... NumberThread: 10 System.out.println("\n=== Exercise 2: Runnable Even Printer ==="); Runnable evenPrinter = createEvenPrinter(); if (evenPrinter != null) { Thread t = new Thread(evenPrinter, "EvenThread"); t.start(); t.join(); } // Expected: 2, 4, 6, ..., 20 System.out.println("\n=== Exercise 3: Sequential Threads ==="); runSequentially(); // Expected: A1..A5 then B1..B5 System.out.println("\n=== Exercise 4: Synchronized Counter ==="); SynchronizedCounter counter = new SynchronizedCounter(); Thread incThread = new Thread(() -> { for (int i = 0; i < 1000; i++) counter.increment(); }); Thread decThread = new Thread(() -> { for (int i = 0; i < 500; i++) counter.decrement(); }); incThread.start(); decThread.start(); incThread.join(); decThread.join(); System.out.println("Counter value: " + counter.getCount()); // Expected: 500 System.out.println("\n=== Exercise 5: Write to File ==="); String writeFile = tempDir + "/output.txt"; List lines = Arrays.asList( "Bismillah", "Advanced Java Programming", "State University of Zanzibar", "IT6003 Exercise" ); writeToFile(writeFile, lines); System.out.println("File written to: " + writeFile); System.out.println("\n=== Exercise 6: Read from File ==="); List readLines = readFromFile(writeFile); if (readLines != null) { System.out.println("Lines read:"); readLines.forEach(line -> System.out.println(" " + line)); } // Expected: same 4 lines as written above System.out.println("\n=== Exercise 7: Count File Stats ==="); int[] stats = countFileStats(writeFile); if (stats != null) { System.out.println("Lines: " + stats[0] + ", Words: " + stats[1] + ", Characters: " + stats[2]); } // Expected: Lines: 4, Words: 10, Characters: ~70 System.out.println("\n=== Exercise 8: Copy File ==="); String copyDest = tempDir + "/output_copy.txt"; copyFile(writeFile, copyDest); System.out.println("File copied to: " + copyDest); List copiedLines = readFromFile(copyDest); if (copiedLines != null) { System.out.println("Copied content matches: " + copiedLines.equals(readLines)); } // Expected: true System.out.println("\n=== Exercise 9: Serialize / Deserialize ==="); String studentFile = tempDir + "/student.ser"; Student student = new Student("Ali Hassan", "SUZA-2024-001", 3.75); serializeStudent(student, studentFile); Student loaded = deserializeStudent(studentFile); System.out.println("Original: " + student); System.out.println("Deserialized: " + loaded); // Expected: same output for both System.out.println("\n=== Exercise 10: ExecutorService Callable ==="); List results = runCallableTasks(); if (results != null) { results.forEach(System.out::println); } // Expected: 5 lines like "Task 1 completed by pool-1-thread-X" // Cleanup temp directory System.out.println("\n--- Cleaning up temp files ---"); Files.walk(Paths.get(tempDir)) .sorted(Comparator.reverseOrder()) .map(Path::toFile) .forEach(File::delete); System.out.println("Done."); } }