Senior Java Developer Full Time Permanent

Semantics 21 is a multi-award-winning UK software company developing specialist desktop software used internationally within public safety and investigative environments. Our technology helps organisations process and review digital evidence more effectively, supporting work that can have genuine real-world impact in areas including child protection and public safety.

We are growing our engineering team and are looking for a Senior Java Software Engineer to help develop large-scale desktop applications used operationally by organisations internationally. Despite the sensitive environments our software supports, development staff are never exposed to illegal or disturbing material as part of their role.

The Role

This is a hands-on software engineering role focused on long-term desktop application development - not web development. You will work across both existing and new applications, contributing to software used daily in real operational environments where reliability, usability, and performance genuinely matter. This role is ideal for someone who enjoys building real software products, solving practical engineering problems, and contributing ideas within a smaller technical team where your voice and technical direction genuinely matter.

You will be involved in:

• Desktop application development using Java and Swing, with some JavaFX where appropriate
• Improving and maintaining large commercial codebases
• Performance optimisation and troubleshooting
• Designing intuitive desktop user interfaces
• Database integration using technologies such as MySQL and SQLite
• File processing, reporting, and data handling
• Contributing ideas, innovation, and long-term technical improvements across the wider platform
• Helping guide development standards, architecture decisions, and future technical direction
• Supporting, mentoring, and where appropriate supervising other developers as the team grows

We use modern development tooling and actively support sensible use of AI-assisted development tools, such as Codex, where they improve productivity, code understanding, testing, or development workflow.

Why Join Us

We are a smaller engineering team where developers are encouraged to contribute ideas, improvements, and innovation - not simply complete assigned tasks. Developers work directly with the CEO within a flat management structure. This gives the development team direct access to someone with hands-on software development, architecture, customer, and investigator experience. Your input will directly influence products, workflows, technical direction, and long-term development decisions across the company. This role suits developers who enjoy building real, long-term software products rather than short-lived web, marketing, or internal dashboard projects.

Key Requirements

• Strong commercial Java development experience
• Experience developing desktop applications using Swing and/or JavaFX
• Strong understanding of Core Java and object-oriented programming
• Experience working within larger or long-term codebases
• Good debugging, analytical, and problem-solving skills
• Ability to work independently and take ownership of technical challenges
• Ability to think beyond individual tickets and contribute to longer-term product improvement
• Strong written and verbal English communication skills

Experience with any of the following would also be beneficial:

• Multithreading/concurrency
• MySQL or SQLite
• JasperReports
• Git
• File parsing and processing
• AI-assisted development workflows

Strong personal projects, GitHub work, or demonstrable practical coding ability are valued more highly than formal qualifications alone. Please include links to previous work, GitHub, portfolio projects, screenshots, or other examples in your CV or application where available.

Working Environment

Based from our Stafford (ST18) office. Office-based preferred, though hybrid working may be considered depending on experience and role fit. Shortlisted candidates will be welcomed into the office as part of the process. Full-time, permanent role. Free onsite parking. We support flexible working hours where possible. Most roles are based around a 7.5-hour working day, Monday-Friday, during normal office hours, with start and finish times agreed around team and business needs.

What We Offer

£35,000 - £45,000 depending on experience, capability, and level of responsibility. Long-term stable product development work. Real influence within a growing engineering team. Direct involvement in product and technical direction. Modern development environment and tooling. Sensible use of AI-assisted development tools. Opportunities for progression and increased technical responsibility over time. Friendly, supportive, and low-bureaucracy working environment.

Important Note

This role is specifically focused on Java desktop software engineering. Applicants focused primarily on web development frameworks are unlikely to be suitable for this position. A formal cover letter is not required, but a short note explaining your relevant Java desktop experience, project examples, or links to previous work is welcome. Direct applicants only - no recruitment agencies.