jtop/report.md

jtop Project Report

Overview

jtop is a terminal-based system monitoring tool written in Java. It provides a lightweight alternative to the top command, featuring a modular and extensible interface.

Features Implemented

• CPU, memory, disk, and network usage monitoring
• Process list with scrollable interface
• Sorting by CPU, memory, PID, name, path, and other headers
• Temperature monitoring (via /sys/class/hwmon or /sys/class/thermal)
• Terminal-size adaptive display
• Keyboard navigation: j/k to scroll, Enter for page scroll, q or Ctrl+C to quit

Class Structure

• Main — Entry point; sets up the terminal and refresh loop
• ShowProcesses — Collects and manages running process data
• ProcessRow — Represents a single process entry
• ProcessTableRenderer — Draws the process table in the terminal
• ProcessSorter — Provides comparators for sorting
• MemoryInfo, CpuInfo, DiskInfo, NetworkInfo, TemperatureInfo, Uptime, etc. — System metrics modules
• Header — Displays header information
• InputHandler — Reads and handles keyboard and mouse input
• TerminalSize — Detects terminal dimensions
• RefreshThread — Handles background refresh of process data
• PathInfo — Retrieves process path and name

Design Considerations

• Modular architecture with clear separation of data collection, rendering, and input handling
• Uses Java 21+ features and the ProcessHandle API
• Layout adapts dynamically to terminal size to prevent overflow
• Graceful handling of missing or inaccessible process information
• Keyboard navigation inspired by tools like less and top

Usage

Compile and run:

javac src/*.java
java src/Main.java

For system-wide installation, use the included build.sh and install.sh scripts.

Keyboard shortcuts:

• j/k: scroll up/down
• Enter: scroll one page
• q or Ctrl+C: quit

Code Quality

• Clear separation of concerns
• Proper encapsulation of fields
• Use of constructors and method overloading where appropriate
• Aggregation/composition used in ShowProcesses and rendering classes
• Interfaces used via Comparator for sorting
• Inheritance applied through Thread extension in RefreshThread

Notes

• JavaDoc documentation can be generated using ./generate_javadoc.sh
• The project is in an alpha stage — some metrics may not work on all hardware
• Tested primarily on Linux systems with Intel and AMD CPUs

TODOs / Known Issues

Tab View

• Planned implementation of a tab system to allow grouping of process information

Config

• Config file support is partially implemented — some fields (e.g., table.header.content) are not yet parsed or applied
• Configs are not yet accessible in system-wide installations

Performance / Design

• On some terminals with custom themes, colors may display incorrectly
• Cursor animations can cause slight lag during refresh
• Table caching occasionally fails, causing unnecessary redraws and performance drops
• On low-performance machines, keyboard input may experience minor delay

Author

• Jürg Georg Hallenbarter
• Version 1.0 — Date: 2025-10-24