Sample work · Code & Bugs
Java: REST interface and a bug fix with regression test
A small task API in Java using pure JDK libraries, tested end-to-end via HTTP, plus an off-by-one error: red before, green after the correction.
Sample work (demo), not a client job. Built as a trial task with invented example data; the check figures below come from the automatic test run and are not polished.
What was built
- REST interface with the JDK web server, creating, reading, updating and deleting tasks
- Compiled without warnings, interface tested via real HTTP calls, even after a restart
- Cross-check with intentionally broken versions: the tests trigger
- Bug fix with regression test, diff and before-after run
Download TaskApi.java Download Rechnung.java Download RechnungTest.java Download bugfix.diff
Pure JDK libraries, no JUnit, no database, no login. Without Spring Boot, Maven and Gradle; tested only against the current Java version, not against older target versions. Work is performed on the source code, not on the customer's server.
How it was checked
Automatic test run on 2026-11-01, taken from the log (test data invented, figures measured):
- javac -Xlint:all -Werror without warnings
- HTTP 40/40 green incl. restart
- Cross-check 3/3 broken versions detected
- Off-by-one bug fix: previously red (exit 1, 3 tests), afterwards green (exit 0, 7 tests)
Limits
What this sample does not cover, so nobody expects more:
- without Spring Boot / Maven / Gradle (frameworks and build tools not approved): customer projects that require them first need approval from the owner
- Java 21 (Temurin) - target versions below 21 (8/11) not tested
- pure JDK libraries (com.sun.net.httpserver), no JUnit, no database, no authentication
- no work on the customer's server without access; result is source code + test proof
Something like this for your business?
Describe briefly what you need. You get a fixed price before I start; nothing happens without your yes.