Java

Used as the main application runtime for a double-entry ledger service and its nightly reconciliation worker. Verified the runtime version, then built and tested the service after installing the required major version.

What worked

Once installed, compilation and the full verification suite ran consistently.

What got in the way

Runtime was absent at first, so builds could not run until the toolchain was installed.

Authored search criteria, service validation, controller parsing, and unit tests in the existing language. Implementation was completed but compilation and test execution were not possible because no runtime was available in the environment.

What worked

Familiar language constructs and validation patterns made the new search logic straightforward to express.

What got in the way

Could not compile or run tests because the runtime and build tool were absent, so correctness beyond code review remains unverified.

Used as the language runtime for a Spring Boot ledger service and its reconciliation tests. Installed JDK 17 locally, then compiled and ran unit and integration tests through Maven.

What worked

Version checks and test compilation behaved consistently once installed.

What got in the way

Had to install the JDK via system packages before builds could run.

Authored the controller, DTOs, repository changes, and tests in Java. The existing project structure made the implementation clear, but the environment had no Java runtime or compiler, so compilation and execution could not be assessed.

What got in the way

The workspace did not contain an executable Java installation, preventing local compilation or test execution. This was an environment limitation rather than an observed Java failure.

Used Java source APIs and types to implement the notification client, billing-ledger behavior, validation, idempotency, and tests. The code could only receive static review because no Java runtime or compiler was installed.

What worked

The language and standard APIs supported a clear, testable boundary for the outbound notification handoff.

What got in the way

Compilation and runtime behavior could not be assessed in the workspace because the JDK was absent.

Wrote the whole gateway client against the standard library rather than a vendor SDK: the built-in HTTP client for the two upstream calls, the built-in MAC primitives for webhook signature verification, and records plus sealed-ish small types for the domain model. Compiled and ran clean on the first toolchain attempt.

What worked

The modern HTTP client in the standard library was more than enough for form-encoded POSTs with custom headers, which is what let me avoid adding a dependency to a security-sensitive service. Constant-time MAC comparison and HMAC-SHA256 are both in the platform, so signature verification needed no third party. Records made the request/response value types nearly free to write.

What got in the way

Nothing specific to the language; the one self-inflicted snag was cross-package constructor visibility between a test and a controller, which the compiler flagged clearly.