JP Morgan Chase Java Interview Questions & Answers
Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About JP Morgan Chase hiring for Java roles
JPMorgan Chase is a global bank offering investment banking, commercial banking, asset management and consumer banking through Chase. Its India corporate centres in Mumbai, Bengaluru and Hyderabad support technology, operations, analytics and risk functions. It hires for software engineers, QA engineers, data analysts, data scientists and quantitative analysts.
For Java roles, this JP Morgan Chase practice set focuses most on JDBC, Hibernate and JPA (7), Java Basics and JVM (7), Collections Framework (5), Strings and Exception Handling (4). It has 7 easy, 18 medium, 5 hard questions, so you can start easy and work up to the harder ones.
Company type
Banking & finance
Headquarters
New York, USA
Main India offices
Mumbai, Bengaluru, Hyderabad
JP Morgan Chase Java interview process
Online assessment (coding + aptitude)
Video interview (HireVue style)
Technical round
Hiring manager round
HR round
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
Solved for JP Morgan ChaseStart practicing
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Access order plus removeEldestEntry gives LRU in a few lines.
class LruCache<K, V> extends LinkedHashMap<K, V> {
private final int capacity;
LruCache(int capacity) {
super(16, 0.75f, true);
this.capacity = capacity;
}
@Override
protected boolean removeEldestEntry(Map.Entry<K, V> e) {
return size() > capacity;
}
}
get and put are O(1).
Empty catches hide failures and make production issues invisible. I would find them with static analysis like SonarQube, then decide per case: handle the error properly, rethrow wrapped with context, or at least log with the stack trace. I would add a global exception handler for APIs and a team rule in code review and lint config to block new empty catch blocks.
04
Write a Spring Data JPA repository method that fetches orders with items to avoid N+1.
Use JOIN FETCH or an entity graph.
public interface OrderRepository extends JpaRepository<Order, Long> {
@Query("select distinct o from Order o join fetch o.items where o.customerId = :cid")
List<Order> findWithItems(@Param("cid") Long customerId);
@EntityGraph(attributePaths = "items")
List<Order> findByStatus(String status);
}
Both load orders and items in one query.
05
Read a large text file line by line efficiently and count lines containing ERROR.
Stream the file lazily so it never loads fully into memory.
Path p = Path.of("app.log");
try (Stream<String> lines = Files.lines(p)) {
long errors = lines
.filter(l -> l.contains("ERROR"))
.count();
System.out.println(errors);
}
try-with-resources closes the file handle. BufferedReader.readLine() in a loop is an equally good option.
06
How do you handle a situation where you made a wrong technical decision?
Situation: I chose eager loading for a reporting entity to save time, and later pages became slow. Task: own and fix it. Action: I told my lead, measured the impact, switched associations to lazy with targeted fetch joins and added query count tests. Result: performance recovered within a sprint and I now review fetch strategy in every design discussion.
Fail-fast iterators, used by ArrayList and HashMap, throw ConcurrentModificationException if the collection is structurally modified during iteration other than through the iterator itself; they check a modCount. Fail-safe or weakly consistent iterators, as in ConcurrentHashMap and CopyOnWriteArrayList, work on a snapshot or tolerate changes and never throw, but may not show the latest updates.
08
Users report the app is slow for the first few minutes after every deployment. Why might this happen?
This is usually JVM warm-up. Code runs in the interpreter until the JIT compiles hot paths, and caches, connection pools and class loading are also cold. Fixes include warm-up traffic before adding the instance to the load balancer, pre-initialising pools, class data sharing (AppCDS) to reduce start time, or newer options like CRaC or GraalVM native image when fast start is critical.
Transient: a new object not yet linked to a persistence context. Managed (persistent): attached to the context, so changes are tracked and flushed automatically through dirty checking. Detached: was managed but the context closed or it was evicted; changes are not tracked until merge(). Removed: scheduled for deletion on flush. persist, merge, detach and remove move entities between these states.
10
What does the var keyword do and where can it not be used?
var, added in Java 10, lets the compiler infer the type of a local variable from its initializer, for example var list = new ArrayList<String>(). Java stays statically typed. var cannot be used for fields, method parameters or return types, and it needs an initializer that is not null. Use it when the type is obvious to keep code readable.
11
Write Java code to reverse an integer without converting it to a string.
Take the last digit with % 10 and build the result, checking for overflow.
public static int reverse(int x) {
long rev = 0;
while (x != 0) {
rev = rev * 10 + x % 10;
x /= 10;
}
if (rev > Integer.MAX_VALUE || rev < Integer.MIN_VALUE) return 0;
return (int) rev;
}
Negative numbers work because % keeps the sign in Java.
12
Describe a time you had to learn a new technology quickly.
Situation: I joined a project using reactive Spring WebFlux with no prior experience. Task: contribute within two weeks. Action: I studied Project Reactor basics, built a small practice service, paired with a senior on my first ticket and kept notes on common operators. Result: I delivered my first feature in the second week and later wrote the team guide on avoiding blocking calls in reactive code.
13
What is the N+1 select problem in Hibernate and how do you fix it?
N+1 happens when you load N parent entities with one query and then a lazy association triggers one extra query per parent, giving N+1 queries. Fix it with a JOIN FETCH in JPQL, an @EntityGraph on the repository method, or batch fetching with @BatchSize or hibernate.default_batch_fetch_size. Detect it by enabling SQL logging or using a query count assertion in tests.
Sealed classes and interfaces, final in Java 17, restrict which classes can extend them using the permits clause, for example sealed interface Shape permits Circle, Square. Each subclass must be final, sealed or non-sealed. This models a closed set of types, and with pattern matching for switch in Java 21 the compiler can check that every case is handled without a default branch.
15
What is the difference between composition and inheritance, and which should you prefer?
Inheritance is an is-a relation where the subclass reuses parent code, but it creates tight coupling and fragile hierarchies. Composition is a has-a relation where a class holds another object and delegates work, such as a Car having an Engine. Prefer composition because it is flexible, allows changing behaviour at runtime and is easier to test. Use inheritance only for a true is-a relationship.
16
Why must you be careful when initial capacity of a HashMap is too small?
If a HashMap starts small and grows large, it resizes many times; each resize allocates a new array and rehashes every entry, which costs CPU and creates garbage. When the expected size is known, use HashMap.newHashMap(n) in Java 19 or later, or set capacity to n divided by 0.75. Too large a capacity wastes memory, so size it to real data.
17
You need to process a 5 GB file using streams without running out of memory. How?
Use Files.lines(path), which reads lazily line by line, inside try-with-resources. Apply filter and map, then aggregate with a collector that keeps small results such as counts or sums instead of collecting all lines into a list. If the output is large, write it incrementally to a BufferedWriter. Avoid sorted() and distinct() on huge data because they buffer everything.
18
Sort a list of employees by department, then by salary descending.
Chain comparators.
employees.sort(
Comparator.comparing(Employee::department)
.thenComparing(Employee::salary,
Comparator.reverseOrder()));
// Streams version returning a new list
List<Employee> sorted = employees.stream()
.sorted(Comparator.comparing(Employee::department)
.thenComparing(Employee::salary, Comparator.reverseOrder()))
.toList();
List.sort is stable, so equal keys keep their order.
19
Explain pattern matching for switch and record patterns in Java 21.
Pattern matching for switch lets a case match on type and bind a variable, such as case Circle c -> Math.PI * c.r() * c.r(). Record patterns deconstruct a record directly: case Point(int x, int y). Guards add conditions with when. With sealed types the compiler checks the switch is exhaustive, so adding a new subtype causes a compile error where it is not handled.
20
A team member compares two Integer values with == and the check fails only for large numbers. Explain.
Integer.valueOf caches objects for values from -128 to 127, so autoboxed small numbers share the same object and == returns true. Larger values create new Integer objects, so == compares two different references and returns false. The fix is to use equals() or compare unboxed int values. Static analysis tools like SonarQube flag this pattern.
Try-with-resources, from Java 7, automatically closes any object that implements AutoCloseable when the try block ends, even if an exception is thrown. Resources close in reverse order of opening. If both the body and close() throw, the close exception is added as a suppressed exception. It replaces long finally blocks for files, JDBC connections and streams.
22
Describe a time you improved the design of existing code.
Situation: our notification module used a 400 line class with switch cases for email, SMS and WhatsApp. Task: add push notifications without breaking anything. Action: I wrote tests for current behaviour, extracted a Notifier interface with one class per channel and used Spring to inject them by type. Result: push was added in one new class, bugs in that module dropped and new channels now take hours, not days.
23
What are the primitive data types in Java and their sizes?
Java has eight primitives: byte (1 byte), short (2), int (4), long (8), float (4), double (8), char (2 bytes, UTF-16 code unit) and boolean (true or false, size JVM dependent). Primitives store values directly and have default values when used as fields, for example 0 for int and false for boolean. Each has a wrapper class such as Integer.
24
You need to add a new payment method to a system that has a big if-else on payment type. How would you redesign it?
This breaks the Open/Closed principle. I would create a PaymentProcessor interface with a pay() method and one implementation per type, such as UpiProcessor and CardProcessor. A factory or a Spring map of beans keyed by type picks the right one. Adding a new method then means adding one new class without touching existing tested code, and each processor can be unit tested alone.
25
Tell me about a time you optimised a slow database query.
Situation: the customer search page took 6 seconds at peak. Task: bring it under 500 ms. Action: I captured the SQL, ran EXPLAIN ANALYZE and found a full scan due to LOWER(email) on an unindexed column and an N+1 on addresses. I added a functional index, fetched addresses with an entity graph and added pagination. Result: response time dropped to 180 ms and database CPU fell by a third.
26
Write a JDBC method to fetch a user by email safely.
HashMap is not thread safe; concurrent writes can lose data or corrupt the structure. ConcurrentHashMap supports full concurrency: reads are lock free and writes use CAS or lock a single bin, so threads rarely block each other. It does not allow null keys or values. It also provides atomic compound operations such as computeIfAbsent and merge, which avoid check-then-act races.
28
A log file shows a NullPointerException only for some users. How do you debug it?
Start with the stack trace; since Java 14 helpful NPE messages name exactly which variable was null. Reproduce with the failing user's data, which often has an optional field missing. Fix the root cause by validating input at the boundary, using Optional for values that may be absent and annotating with @NonNull. Add a unit test for that data case so it does not return.
29
What is a ClassLoader and what is the delegation model?
A ClassLoader loads .class files into the JVM. The main loaders are Bootstrap (core classes), Platform (formerly Extension) and Application (classpath). In the parent delegation model a loader first asks its parent to load a class and only loads it itself if the parent cannot. This prevents user code from replacing core classes like java.lang.String.
The heap stores all objects and is shared by threads; it is managed by the garbage collector. Each thread has its own stack holding frames with local variables and partial results. Metaspace (native memory since Java 8) stores class metadata. There are also the program counter register and native method stacks. StackOverflowError comes from the stack and OutOfMemoryError usually from heap or metaspace.
Tips to crack the JP Morgan Chase Java interview
Practise recorded video interview answers, keeping responses structured and within time limits.
Learn banking basics like payments, loans, KYC and risk controls for domain questions in technology and analytics roles.
Look up the Code for Good hackathon and JPMorgan's technology programmes if you are applying as a student or fresher.
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; JP Morgan Chase interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the JP Morgan Chase Java interview?
Candidates usually go through 5 stages: Online assessment (coding + aptitude); Video interview (HireVue style); Technical round; Hiring manager round; 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 JP Morgan Chase Java interview?
This practice set leans on JDBC, Hibernate and JPA (7), Java Basics and JVM (7), Collections Framework (5), Strings and Exception Handling (4). Revise those first, then practise explaining one or two of your own projects end to end, because most JP Morgan Chase interviewers ask you to walk through real work.
Are these the exact questions asked at JP Morgan Chase?
No. These are curated practice questions that match the skills and difficulty usually tested in banking & finance interviews like JP Morgan Chase's. They are not a leaked or verified list of past questions.
Where does JP Morgan Chase hire Java professionals in India?
JP Morgan Chase has large teams in Mumbai, Bengaluru, Hyderabad. Openings and locations change often, so check the JP Morgan Chase careers page and filter by city and experience.