🚀 Priority Job Scheduler (Custom 3-ary Heap)

The Priority Job Scheduler is a console application in Java designed to manage and dispatch tasks based on their effective priority.
Its core feature is a custom implementation of a 3-ary Max Heap, demonstrating strong understanding of data structures, OOP principles, and exception handling.

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✨ Key Features

• Polymorphic Task Management:
  Includes BugFix and FeatureRequest classes inheriting from an abstract Task base class.

• Dynamic Prioritization:
  BugFix tasks automatically get a priority boost, ensuring that critical issues are handled before lower-impact tasks.

• Queue Operations:

  • PEEK – preview the next task without removing it
  • POP – complete and remove the highest-priority task

• Custom Exceptions:
  Includes InvalidTaskDataException and EmptyQueueException for clean error control flow.

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🧠 Data Structure Logic: 3-ary Max Heap

Standard heaps are typically binary (2 children per node). This project implements a 3-ary Heap (d-ary heap where d=3), which offers specific performance trade-offs and structural differences.

How it works?

In a 3-ary heap, the tree is flatter than a binary heap because each node can hold up to 3 children. This reduces the height of the tree ($\log_3 n$ vs $\log_2 n$).

Array Representation Logic

Since the heap is implemented using a flat array, we use specific formulas to navigate relations between nodes:

Relation	Formula (for index i)
Parent	(i - 1) / 3
Child 1	3 * i + 1
Child 2	3 * i + 2
Child 3	3 * i + 3

Performance Trade-offs

• ✅ Faster Insertions (Push): Due to the lower tree height, "bubbling up" a new element requires fewer comparisons.
• ⚠️ Slower Deletions (Pop): "Bubbling down" is slightly more complex, as the algorithm must compare 3 children (instead of 2) to find the largest one to swap with.

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🛠️ Technology Stack

• Language: Java 17+
• Build Tool: Apache Maven
• Testing: JUnit 5 (Jupiter)
• Data Structure: Custom 3-ary Max Heap implementation

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🧱 Project Structure

This project follows standard Maven directory layout:

PriorityJobScheduler/
├── pom.xml                   # Maven configuration
└── src/
  ├── main/
  │   └── java/
  │       ├── app/          # Main console application
  │       ├── logic/        # Scheduler logic (wrapper around the heap)
  │       ├── model/        # Task, BugFix, FeatureRequest
  │       ├── exceptions/   # Custom exceptions
  │       └── structures/   # MaxHeap interface & Array3Heap implementation
  └── test/
      └── java/
          └── tests/        # JUnit 5 tests (SchedulerTest.java)

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🚀 Getting Started (Local Setup)

This project uses Maven for building and dependency management.

1️⃣ Prerequisites

Make sure you have installed:

• Java JDK 17 or later
• Apache Maven
  Check installation with:

  mvn -v

2️⃣ Compile the Project

Open a terminal in the project root directory (where pom.xml is located) and run:

mvn clean install

This will: -Clean previous builds -Compile the project -Run all unit tests

3️⃣ Run the Application

After building, run the console application using:

java -cp target/priority-scheduler-1.0-SNAPSHOT.jar app.ConsoleApp

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🧪 Testing

All major functionality—including scheduler logic and the custom heap—is covered with JUnit 5 tests. Run tests with:

mvn test