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Building a Multithreaded Task Scheduler in Java

Explore a Java program that efficiently schedules and executes tasks using multithreading. With a robust structure, the code reads tasks from an input file, assigns them to threads, simulates task execution, and logs results. Leveraging nested classes like TaskScheduler and TaskThread, each task executes concurrently. Synchronization is ensured through a Monitor class for processor access and a lock for log writing. This multithreaded approach enhances performance, providing a practical example of efficient task management in Java.

Understanding Multithreading in Java for Task Management

This Java program showcases a multithreaded task scheduler designed to efficiently manage and execute tasks concurrently. The code reads task details from an input file, assigns them to separate threads, simulates task execution with synchronized processor access, and logs results systematically. Employing nested classes like TaskScheduler and TaskThread optimizes task execution. This example illustrates effective task management through multithreading, making it a valuable resource for anyone studying concurrent programming in Java. Whether you're delving into Java assignments or seeking insights into multithreading, this code provides a practical foundation to help with your Java assignment.

Block 1: Imports and Class Declaration

import java.io.*; import java.util.*; import java.text.*; public class P3 { // Class members and constants... }

This block includes necessary imports and declares the main class (P3). The class includes a DateFormat for formatting dates, a lock object for logging synchronization, a main method, and several nested classes (TaskScheduler, TaskThread, Task, and Monitor).

Block 2: Date Format and Log Lock

private static final DateFormat dateFormat = new SimpleDateFormat("EEE MMM dd HH:mm:ss z yyyy"); private static final Object logLock = new Object();

These lines define a date format and a lock object for logging synchronization. SimpleDateFormat is used for formatting dates.

Block 3: Main Method

public static void main(String[] args) throws Exception { // Command-line argument validation... System.out.println("Server initialised...."); // Read tasks from input file and start a thread for each task... }

Block 4: TaskScheduler Class

static class TaskScheduler implements Runnable { // TaskScheduler members... }

This nested class represents a task scheduler. It implements Runnable and takes a Task as a parameter. It reads inputs for the task and creates TaskThread instances for each input.

Block 5: TaskScheduler Run Method

@Override public void run() { // Read inputs, create a monitor, and start a thread for each input... }

In the run method of TaskScheduler, inputs for the task are read, a Monitor is created, and a new thread (TaskThread) is started for each input.

Block 6: TaskThread Class

static class TaskThread implements Runnable { private String taskFilename; private int threadNo; private int input; private Monitor monitor; public TaskThread(String taskFilename, int threadNo, int input, Monitor monitor) { this.taskFilename = taskFilename; this.threadNo = threadNo; this.input = input; this.monitor = monitor; }

This completion includes the constructor for TaskThread that initializes its fields, and the run method, which simulates a delay based on the input, acquires a processor using the Monitor, performs a computation, writes to the log, and releases the processor.

Block 7: TaskThread Run Method

@Override public void run() { try { // Simulate the delay Thread.sleep(input * 100); // Get access to processor using monitor monitor.acquireProcessor(); int result = input * input; // Add to the log writeToLog(taskFilename, threadNo, input, result); monitor.releaseProcessor(); } catch (InterruptedException e) { e.printStackTrace(); }

This run method simulates a delay based on the input, acquires a processor using the Monitor, performs a computation (squaring the input in this case), writes the result to the log, and releases the processor. The method catches InterruptedException and prints the stack trace if the thread is interrupted during sleep.

Block 8: WriteToLog Method

private static void writeToLog(String taskFilename, int threadNo, int input, int result) { // Synchronized block for logging... }

This method writes log entries in a synchronized manner. It includes information about the task filename, thread number, input, and result.

Block 9: ReadTaskList Method

private static List readTaskList(String filename) { // Read tasks from file and return a list... }

This method reads tasks from the specified file, creates Task objects, and returns a list of tasks.

Block 10: Task Class

static class Monitor { private int availableProcessors; public Monitor(int processors) { this.availableProcessors = processors; }

Block 11: Monitor Methods

public synchronized void acquireProcessor() throws InterruptedException { while (availableProcessors <= 0) { wait(); } availableProcessors--; } public synchronized void releaseProcessor() { availableProcessors++; notify(); }

The Monitor class includes methods for acquiring and releasing processors in a synchronized manner. The acquireProcessor method waits until a processor is available, and the releaseProcessor method releases a processor and notifies waiting threads.


In conclusion, delving into the intricacies of this multithreaded task scheduler illuminates the power of concurrent programming in Java. The synchronized execution of tasks through threads not only optimizes performance but also serves as a valuable learning resource for individuals exploring the realms of Java programming. Whether you're a student seeking insights into multithreading concepts or someone tackling a Java assignment, this example provides practical knowledge and a solid foundation. Mastering multithreading is essential for crafting efficient and responsive software applications, and the presented code offers a hands-on approach to comprehending this critical aspect of Java development. Embrace the possibilities of concurrent programming as you navigate the dynamic landscape of Java applications.