Capgemini Java Full Stack with React Interview Questions & Answers
Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About Capgemini hiring for Java Full Stack with React roles
Capgemini is a French multinational IT services and consulting group providing technology, engineering, cloud and data services. India is its largest employee base, supporting projects in testing, application development, SAP, data engineering and analytics for global clients. It hires freshers as analysts and software engineers, and experienced professionals in QA automation, data and cloud roles.
For Java Full Stack with React roles, this Capgemini practice set focuses most on REST APIs, Security and Microservices (7), Collections and Streams (6), Core Java (6), Spring Boot (5). It has 15 easy, 15 medium questions, so you can start easy and work up to the harder ones.
Company type
IT services
Headquarters
Paris, France
Main India offices
Mumbai, Bengaluru, Pune, Chennai, Hyderabad
Capgemini Java Full Stack with React interview process
Online assessment (pseudocode + English)
Game-based aptitude test
Technical interview
HR round
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
Solved for CapgeminiStart practicing
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An API gateway, such as Spring Cloud Gateway, is the single entry point for clients. It handles routing, authentication, rate limiting, CORS and request logging. Service discovery lets services find each other without hard-coded addresses: with Eureka or Consul, services register themselves, and clients look them up. On Kubernetes, built-in Services and DNS usually replace a separate discovery server, and an ingress or gateway handles external traffic.
Comparable defines a class's natural ordering through compareTo, implemented inside the class itself, such as String or Integer. Comparator is a separate object with compare, so you can define many orderings without changing the class. Since Java 8, Comparator.comparing, thenComparing and reversed make multi-field sorting concise. Use Comparable for one obvious order and Comparator for business-specific sorting like price then rating.
useMemo caches the result of an expensive calculation until its dependencies change, such as filtering and sorting a big list. useCallback caches a function reference, which matters when passing callbacks to children wrapped in React.memo or used in effect dependencies. Do not wrap everything, because memoization itself has a cost. The React Compiler, released as stable in 2025, can add much of this memoization automatically in supported projects.
06
Write code that runs tasks in parallel using ExecutorService and collects results.
Situation: after a release, our login API started returning 500 errors at peak time. Task: as the on-call developer I had to restore service fast. Action: I checked logs and metrics, found the new connection pool settings were too small, rolled back the config and informed stakeholders. Then I led the root cause review and added a load test to the pipeline. Result: service recovered in 20 minutes and the issue never repeated.
The JVM runs Java bytecode and handles memory, garbage collection and JIT compilation. The JRE is the JVM plus core class libraries needed to run programs. The JDK is the JRE plus development tools such as javac, jar, jshell and jdb. Since Java 11 a separate JRE is no longer shipped by Oracle, so developers install a JDK such as Temurin or Oracle JDK 17 or 21 and build smaller runtimes with jlink if needed.
09
Find the second highest salary from a list of employees using streams.
static boolean isPalindrome(String s) {
String clean = s.replaceAll("\\s+", "").toLowerCase();
int i = 0, j = clean.length() - 1;
while (i < j) {
if (clean.charAt(i++) != clean.charAt(j--)) {
return false;
}
}
return true;
}
// Two pointers give O(n) time and O(n) space for the cleaned copy.
// isPalindrome("Nurses Run") returns true.
12
Write a basic CRUD REST controller in Spring Boot.
200 OK for successful reads and updates, 201 Created with a Location header after creating a resource, and 204 No Content for successful deletes. 400 Bad Request for validation errors, 401 Unauthorized when authentication is missing or invalid, 403 Forbidden when the user is authenticated but not allowed, 404 Not Found, 409 Conflict for version or duplicate conflicts, and 429 Too Many Requests for rate limits. 500 means an unexpected server error and 503 means temporarily unavailable.
REST treats everything as a resource identified by a URL, such as /api/orders/42, and uses standard HTTP methods to act on it. Requests are stateless, so each one carries all the information needed, including the auth token. Responses use proper status codes and representations, usually JSON, and can be cacheable. Good REST design uses nouns in URLs, plural resource names, nested paths for relations and query parameters for filtering and pagination.
15
What is the difference between checked and unchecked exceptions?
Checked exceptions extend Exception (but not RuntimeException) and must be caught or declared with throws, for example IOException or SQLException. Unchecked exceptions extend RuntimeException, such as NullPointerException or IllegalArgumentException, and the compiler does not force handling. Use checked exceptions for recoverable conditions the caller should handle, and unchecked ones for programming errors. Spring prefers unchecked exceptions, for example DataAccessException, to keep service code clean.
16
Explain Inversion of Control and Dependency Injection.
Inversion of Control means the framework, not your code, creates and wires objects. Dependency Injection is how Spring does it: a class declares what it needs, usually through its constructor, and the container supplies the beans. For example, OrderService receives an OrderRepository instead of creating one with new. This reduces coupling, makes it easy to swap implementations and lets you pass mocks in unit tests.
HashMap stores entries in an array of buckets. The key's hashCode is spread and masked to find a bucket index. Collisions are kept in a linked list, and since Java 8 a bucket converts to a red-black tree after 8 entries when capacity is at least 64, giving O(log n) worst case. When size exceeds capacity times load factor 0.75, the table doubles and entries are redistributed. get uses hashCode to find the bucket and equals to find the key.
18
What is the difference between == and === in JavaScript?
== compares after type coercion, so 0 == '0' and null == undefined are true, which leads to surprising results. === compares both type and value without coercion, so 0 === '0' is false. Always use === and !== in application code. The only common exception is value == null, which checks for both null and undefined in one expression.
19
You need a thread-safe singleton for a configuration loader. How do you implement it?
The simplest safe options are an enum singleton or the holder idiom. With the holder idiom, a private static nested class holds the instance, and the JVM's class loading guarantees lazy, thread-safe initialisation without synchronization. Double-checked locking also works but needs a volatile field. In a Spring application you usually do not write singletons at all, because beans are singleton-scoped by default and the container manages them.
20
Write CSS for a product grid that shows 1 column on mobile, 2 on tablet and 4 on desktop.
Create application-dev.yml, application-test.yml and application-prod.yml, each with its own spring.datasource URL, username and driver. Keep shared settings in application.yml. Activate the right one with SPRING_PROFILES_ACTIVE in each environment. Read production credentials from environment variables, for example url: ${DB_URL}, instead of hard-coding them. For realistic integration tests, Testcontainers can start the same database engine used in production.
22
Your application fails at startup with a circular dependency error between two services. What do you do?
Spring Boot 2.6 and later forbid circular references by default. The real fix is design: two services depending on each other usually means a responsibility is in the wrong place. Extract the shared logic into a third bean, or use an application event so one service notifies the other without a direct reference. Using @Lazy or allowing circular references in properties hides the problem and should only be a temporary workaround.
23
What is the difference between authentication and authorization?
Authentication verifies who the user is, for example by checking a password, OTP or token. Authorization decides what that authenticated user is allowed to do, for example only admins can delete products. In Spring Security, authentication produces an Authentication object with granted authorities, and authorization uses those authorities in URL rules or annotations like @PreAuthorize("hasRole('ADMIN')"). A failed authentication gives 401 and a failed authorization gives 403.
Events bubble up from the target element to its ancestors. With event delegation you attach one listener to a parent, such as a ul, and use event.target.closest('li') to find which child was clicked. This saves memory compared with a listener on every item and automatically works for items added later. It is commonly used for dynamic tables and lists. React uses a similar idea by attaching listeners at the root.
25
What is a functional interface and how do lambdas relate to it?
A functional interface has exactly one abstract method, such as Runnable, Comparator, Function, Predicate, Supplier or Consumer, and can be marked with @FunctionalInterface. A lambda expression is a short implementation of that single method, for example Predicate<String> empty = s -> s.isBlank(). Method references like String::toUpperCase are an even shorter form. Lambdas power the Streams API and callback-style code.
26
Write a production-friendly Dockerfile for a Spring Boot application.
mappedBy marks the inverse side and names the field on the other entity that owns the relationship. The owning side, usually the @ManyToOne with the foreign key column, is the one Hibernate uses to write the join column. For example, Order has @OneToMany(mappedBy = "order") and OrderItem has @ManyToOne @JoinColumn(name = "order_id"). Always update both sides in helper methods such as addItem to keep the object graph consistent.
The GC frees objects that are no longer reachable from GC roots such as thread stacks and static fields. Most objects die young, so the heap is generational: minor collections clean the young generation often and survivors are promoted. G1 is the default collector since Java 9 and targets predictable pause times by collecting regions. ZGC and Shenandoah offer sub-millisecond pauses for large heaps. Tuning usually starts with -Xmx and choosing the collector, not dozens of flags.
ArrayList is backed by a resizable array, giving O(1) random access and good cache locality, and appending is amortised O(1). LinkedList is a doubly linked list with O(1) insertion at known nodes but O(n) access by index and more memory per element. In practice ArrayList is faster for almost all workloads. For queue or stack behaviour, ArrayDeque is usually better than LinkedList.
30
What is the difference between persist and merge, and between save and saveAndFlush?
persist makes a new entity managed and assigns its ID; it fails for detached entities. merge copies the state of a detached entity onto a managed copy and returns that copy. Spring Data save calls persist for new entities and merge otherwise. saveAndFlush also calls flush, pushing pending SQL to the database immediately, which helps when you need a constraint error or trigger result now. The commit still happens at the end of the transaction.
Tips to crack the Capgemini Java Full Stack with React interview
Practise game-based cognitive tests and pseudocode questions, which are commonly part of Capgemini's online assessment.
Prepare a short explanation of your projects, focusing on your role, tools used and what you would improve.
Learn about Capgemini's engineering arm and its work in sectors like automotive and financial services to show interest.
Keep a one-minute story ready for every project on your CV: problem, your part, tools, result.
Practise the hard questions on this page aloud; Capgemini interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the Capgemini Java Full Stack with React interview?
Candidates usually go through 4 stages: Online assessment (pseudocode + English); Game-based aptitude test; Technical interview; HR round. The exact rounds change with the role, team, location and your experience, so confirm the process with the recruiter.
Which topics should I prepare for the Capgemini Java Full Stack with React interview?
This practice set leans on REST APIs, Security and Microservices (7), Collections and Streams (6), Core Java (6), Spring Boot (5). Revise those first, then practise explaining one or two of your own projects end to end, because most Capgemini interviewers ask you to walk through real work.
Are these the exact questions asked at Capgemini?
No. These are curated practice questions that match the skills and difficulty usually tested in it services interviews like Capgemini's. They are not a leaked or verified list of past questions.
Where does Capgemini hire Java Full Stack with React professionals in India?
Capgemini has large teams in Mumbai, Bengaluru, Pune, Chennai, Hyderabad. Openings and locations change often, so check the Capgemini careers page and filter by city and experience.
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