How to Hire a Java Developer in 2026: Spring Boot, Virtual Threads, and the Screen That Works

Java is one of the highest-volume hiring categories and one of the most inconsistently screened. The language has a 30-year history, which means the talent pool spans developers who learned Java in the early 2000s through people who picked it up for Spring Boot last year. A job posting that just says “Java experience required” can attract all of them.

The screen needs to establish which version of Java the candidate knows and which version your project needs.

Java 21 is the current baseline

Java 21 LTS shipped in September 2023. It brought three changes that matter for day-to-day development: virtual threads (Project Loom, finally stable), pattern matching for switch expressions (stable after preview cycles), and sequenced collections.

Spring Boot 3.x, released in late 2022, requires Java 17 minimum and encourages Java 21. If your team runs Spring Boot 3, asking about Spring Boot 2 patterns is testing the wrong thing. The two versions differ in how they handle Jakarta EE (the package rename from javax.* to jakarta.* was Spring Boot 3’s most disruptive change), native image support via GraalVM, and observability.

Start the screen by asking what Java version the candidate uses daily and what the significant additions were. A developer who cannot name anything meaningful from Java 11-21 has either been stuck on Java 8 or is learning by reading rather than building.

Virtual threads: what changes and what does not

Virtual threads are the most significant Java feature in many years, and their implication is often misunderstood in both directions.

Ask: “What problem do virtual threads solve, and what kind of workload benefits from them?”

The answer: traditional Java threads map 1:1 to OS threads, which are expensive. Creating 10,000 platform threads is impractical. This limitation forced reactive programming frameworks (Project Reactor, RxJava) on teams that needed high concurrency on IO-bound work. Virtual threads are JVM-managed, not OS-managed, and are cheap enough to create per-task. For a service that handles 10,000 concurrent requests, each waiting on a database or HTTP response, you can now write blocking code and let the JVM park virtual threads cheaply rather than needing to learn reactive streams.

The important nuance: virtual threads do not help CPU-bound work. If your task is number-crunching, encryption, or image processing, virtual threads won’t improve throughput. The same number of CPU cores is still the limit. A candidate who says “virtual threads make everything faster” has not thought it through.

Ask a follow-up: “If you were migrating a Spring Boot 2 application using reactive Reactor to Spring Boot 3 with virtual threads, what would you look for?” The answer should mention: blocking operations inside reactive pipelines that can now be replaced with straightforward blocking code; thread-local variables that virtual threads may interact with differently; the spring.threads.virtual.enabled=true property in Spring Boot 3.2+. A developer who has actually done this migration will have specifics.

Spring Boot and the dependency injection screen

Spring Boot is the dominant Java web framework. Regardless of the other skills on the job description, if the role involves building HTTP services in Java, Spring Boot knowledge is probably expected.

Ask: “How does Spring Boot’s dependency injection work, and what is the difference between @Component, @Service, @Repository, and @Controller?”

The answer: Spring scans the classpath for annotated classes and registers them as beans. @Component is the generic annotation. @Service, @Repository, and @Controller are specializations that carry semantic meaning and sometimes additional behavior (@Repository enables exception translation; @Controller registers the class for request mapping). Beans are injected via constructors, setters, or field injection. Constructor injection is the recommended style because it makes dependencies explicit and the class testable without a Spring context.

Follow up: “What is Spring Boot auto-configuration and what problem does it solve?” Auto-configuration inspects the classpath and the application properties, and wires up beans that match what it finds. If spring-boot-starter-data-jpa is on the classpath, Spring Boot configures a DataSource, EntityManagerFactory, and transaction manager automatically. This eliminates the XML or Java config boilerplate that older Spring required. A developer who understands auto-configuration can debug startup failures, not just run the happy path.

The Stream API as a practical filter

The Stream API and lambdas shipped with Java 8 in 2014. In 2026, a candidate who still writes a for loop to filter a list of objects has not kept pace with the language that they are selling as their expertise.

Ask them, in a screen, to write code that takes a list of orders, filters for orders placed in the last 30 days with a total above $100, and returns a list of customer IDs, sorted and with duplicates removed:

List<String> recentHighValueCustomers = orders.stream()
    .filter(o -> o.getDate().isAfter(LocalDate.now().minusDays(30)))
    .filter(o -> o.getTotal().compareTo(BigDecimal.valueOf(100)) > 0)
    .map(Order::getCustomerId)
    .distinct()
    .sorted()
    .collect(Collectors.toList());

You are not looking for perfect syntax. You are looking for whether they think in streams or whether they reach for a loop and build up a HashSet by hand. The latter is not wrong, but it signals someone who learned Java before 8 and has not adjusted their idioms.

Follow up with: “What is the difference between map and flatMap on a Stream?” Map applies a function that produces one output per input. FlatMap applies a function that produces a Stream per input and then flattens all those streams into one. A developer who has worked with nested collections (a list of orders each with a list of items) will know flatMap from real use.

Records and newer language features

Java 16 made records final. Records are concise, immutable data carriers:

public record CustomerSummary(String id, String name, BigDecimal total) {}

This gives you an immutable class, constructor, accessors, equals, hashCode, and toString in one line. A candidate building DTOs, request/response objects, or domain value types should reach for records by default in 2026. If they are still writing full POJO classes with getters and builders for simple data objects, ask why.

Pattern matching for instanceof (stable since Java 16) and pattern matching for switch (stable in Java 21) are also worth probing. The switch expression form:

String description = switch (shape) {
    case Circle c -> "Circle with radius " + c.radius();
    case Rectangle r -> "Rectangle " + r.width() + "x" + r.height();
    default -> "Unknown shape";
};

A developer who has not followed the language’s evolution will write a series of if (shape instanceof Circle) checks with casts. Both work. One is idiomatic modern Java.

What Java developers look for

Java engineers often prioritize stability: long LTS release cycles, mature frameworks, and good tooling support in IDEs. They are less likely to be drawn to a role by “we use cutting-edge tech” and more by “we have interesting problems and a well-maintained codebase.”

If your codebase is well-tested, has clear module boundaries, and uses current Spring Boot idioms, say so in the job description. Java engineers respond to operational maturity signals.

Roles that push Java engineers away: unclear ownership, a Spring Boot 2 codebase with no migration plan, and “we move fast” cultures where skipping tests and ignoring technical debt are normalized. The Java community broadly values discipline. A hiring process that signals the opposite will lose good candidates at the offer stage.

For adjacent hiring, the Go developer hiring guide covers the language that has taken the most ground from Java in infrastructure and cloud-native services. The vetted developer guide covers the general screening framework that the language-specific guides build on.