Vesa Saarinen, Solution Architect & Software Developer, Portfolio

Cobol to Java modernizer

Converts legacy Cobol programs into modern Java. A grammar-driven parser and multi-stage AST pipeline produce runtime-correct Java. LLM stages then modernize the output into records, streams and clean naming, with an optional profile-guided performance pass on hot methods. An integration test suite checks each stage against the Cobol reference.

Why: Explore compiler construction, grammar-driven parsing, and bridging legacy business logic to a modern runtime.

Example: Cobol → Java → LLM-modernized Java

Java

arch-audit

An architecture auditing tool that speeds up getting oriented in an unknown codebase. It combines Semgrep static analysis, OSV dependency scanning, Tokei code metrics, and tree-sitter structure extraction into an interactive terminal-based findings browser. An optional LLM stage adds risk explanations and remediation guidance per finding.

Why: Explore DevSecOps tooling and LLM-assisted code review.

Python

Neural networks and automatic differentation in Java

Neural networks with automatic differentiation and backpropagation in Java from scratch.

Why: Learn about machine learning, gradient descent, neural networks.

Github: https://github.com/vesas/java-nn

Java

Omastoppi.fi

Web/mobile application for quickly viewing departure times for nearby public transport stops. Data fetched realtime from the HSL GraphQL API.

Why: Learn React/Next.js, and create an application which can be used quickly when on the go on the HSL region.

Release: https://www.omastoppi.fi/

Github: https://github.com/vesas/nextjs-omastoppi

React/Next.js

Econstats.eu

Application which charts the major macroeconomic indicators for the EU and US areas. Data is fetched every day from the Eurostat and FRED APIs.

Why: Learn more about AWS services. Create an economy "dashboard" for myself.

Release: https://econstats.eu

Architecture: https://econstats.eu/architecture

Python AWS

WFC generator

In game development WFC (Wave Function Collapse) is used for generating output based on a set of tiles and rules. This output can then be used for different purposes, like level or texture generation. Here I'm creating textures. This is a simple Java implementation of Wave Function Collapse algorithm where the rules are defined in code.

Why: Complex result from simple rules.

Github: https://github.com/vesas/simple-wfc

Java