Learn CHEERPJ with Real Code Examples
Updated Nov 25, 2025
Practical Examples
Running legacy educational Java applets
Java-based CAD tools inside browser
Internal enterprise Swing dashboards
Java crypto or math libraries in JS projects
Browser-based code editors or simulators
Troubleshooting
Check console for missing class errors
Ensure all JAR dependencies are included
Preload resources to reduce launch times
Enable caching for large Wasm binaries
Use debug mode for diagnosing runtime failures
Testing Guide
Use Java unit tests before porting
Test popups and UI logic in browser
Check for missing Java classes
Profile loading time with DevTools
Test app in multiple browsers
Deployment Options
Static web hosting
Enterprise intranet deployments
CDN delivery with caching
Bundle into SPAs
Hybrid: Backend Java + Frontend CheerpJ
Tools Ecosystem
CheerpJ AOT compiler
CJRE Runtime
HTML5 canvas rendering engine
Browser DevTools for debugging
Java tooling (javac, jarsigner, etc.)
Integrations
JavaScript via interop functions
HTML canvas for rendering
Web APIs for network requests
Backend Java servers
Any existing JVM library
Productivity Tips
Keep JAR dependencies light
Use AOT compilation for speed
Profile startup and reduce class loading
Use browser caching for Wasm runtime
Test frequently in multiple browsers
Challenges
Large Wasm binaries
Mapping Java UI events to JS
Handling multi-jar dependency chains
Ensuring responsive performance
Debugging bytecode-level errors