Where Java is used
End users rarely see Java: it works behind the scenes, on servers. Typical use cases:
- banking, payments and insurance, where accurate calculations and long data history matter;
- logistics and distribution: warehouses, routing, data exchange with carriers and partners;
- enterprise accounting and document management systems and internal portals at large companies;
- backends for mobile apps and web services with large user bases;
- processing large data and event streams in real time.
Java was also the primary language for Android apps, and many mobile projects still contain Java code.
Java advantages
- Reliability and predictability. Strong typing catches many errors before the program runs, not in production.
- A long lifecycle. Java takes compatibility seriously: code written many years ago often runs on new versions with minimal changes.
- A huge ecosystem. Mature libraries proven at large companies exist for message queues, databases, security and reporting.
- Scalability. Java makes good use of powerful servers and lets you distribute load across many machines.
- A deep talent pool. There are plenty of Java developers, so you're not dependent on a single team to maintain the system.
Java drawbacks
- Lots of code. Java is verbose: what takes one line in other languages can take several here. Small features take longer to build.
- Resource-hungry. A Java service usually needs more memory and starts more slowly than a Go equivalent. For small cloud services, this shows up on the bill.
- Overkill for simple projects. A corporate website or small online store in Java means overpaying for development and support with no tangible benefit.
- Complex history in legacy systems. Many Java systems carry years of changes by different teams, which makes them hard to untangle.
When to consider alternatives
- If you like Java's reliability but want more concise code, take a look at Kotlin. It runs on the same runtime and can be introduced into a Java project gradually, alongside existing code.
- If your company runs on the Microsoft ecosystem (Windows servers, Azure, Microsoft accounts for employee sign-in), C# on Microsoft's platform is the more logical choice.
- For small, fast services with minimal resource usage, it's worth comparing Java with Go.
Java versions and frameworks
Java evolves on a regular cadence, and some versions receive long-term support (LTS); these are the ones used in production. Many companies still run Java 8. It's stable, but modern libraries are gradually dropping support for it, and upgrading gets more expensive every year.
For new projects, we use Spring Boot, the most popular framework for server-side Java applications, with Hibernate for database access. We package projects in Docker containers, which simplifies deployment and upgrades on any infrastructure.
New development or working with an existing system
A new Java system is almost always a large project, so we start with design: modules, boundaries between them, data exchange formats and load requirements. It's often wise to start with a single well-structured system and split it into separate services only when there's a real need.
An existing system is a different story. Rewriting it from scratch is usually too risky: the code holds years of business rules nobody remembers anymore. We take a gradual path: upgrade the Java version and dependencies, cover critical areas with tests and replace problem modules one at a time. Learn more about this approach on our legacy system modernization page.
Integrations and data exchange
Large systems almost never work in isolation. Java services typically exchange data with ERPs, CRMs, banks, warehouse management systems and websites. For reliable data exchange, we use message queues: if one system is temporarily unavailable, data isn't lost but waits its turn.
Security, access control and audit logs
Enterprise systems store data that can't be lost or shown to the wrong people: contracts, payments, customers' personal data. That's why we build in from day one:
- permissions down to individual actions and records, not just menu sections;
- sign-in with corporate accounts if the company already has single sign-on;
- an audit log: who changed what in critical data, and when;
- regular scanning of libraries for known vulnerabilities and timely updates.
We discuss your security team's requirements at the start, because adding them to a finished system is always harder.
What affects cost
- Scale and number of modules: how many processes and departments the system covers.
- Reliability requirements: whether downtime is acceptable, and how many users and how much data are expected.
- Integrations: the number of external systems and the maturity of their APIs.
- Security and audit: activity logs, access control, the client's security team requirements.
- State of the existing code: Java version, documentation, tests, the number of outdated libraries.
We break large projects into phases, each delivering a working result. That keeps the budget under control and lets you adjust priorities along the way.
FAQ
Isn't Java an outdated language? No. The language is actively evolving, and new versions are released regularly. Many large systems around the world continue to be developed in Java.
Our system runs on Java 8. Do we need to upgrade? We recommend planning an upgrade: new libraries and security fixes are gradually being discontinued for older versions. We do it in phases, with tests.
Can we add Kotlin to our Java project? Yes, they work together in the same project. New modules can be written in Kotlin without touching the existing code.
Is Java a good fit for a startup? Sometimes, if the product is complex from the start and designed for heavy load. But to validate an idea, faster-to-develop technologies are often more practical.
Why Promodex
Large systems require staying power, and our experience helps: 750+ projects since 2015. Promodex developers are full-time, in-house specialists, and you can see what's being done at every stage. We align phases, reporting and the engagement model with your company's processes, and after launch we remain responsible for supporting and evolving the system.
