Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About Zoho hiring for Java roles
Zoho is an Indian software company offering a suite of business applications including Zoho CRM, Zoho Books, Zoho Mail and Zoho Creator. It is privately held and builds most of its technology in-house. It hires for software developers, QA engineers and technical support roles, with a selection process known for programming-heavy rounds.
For Java roles, this Zoho practice set focuses most on JDBC, Hibernate and JPA (5), Collections Framework (5), Java Basics and JVM (5), OOP in Java (5). It has 2 easy, 18 medium, 10 hard questions, so you can start easy and work up to the harder ones.
Company type
Product
Headquarters
Chennai, India
Main India offices
Chennai, Tenkasi
Zoho Java interview process
Written test (aptitude + C programming output)
Basic programming round
Advanced programming round
Technical interview
HR round
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
Solved for ZohoStart practicing
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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.
02
You have to process tasks in order of priority. Which collection do you use?
Use PriorityQueue, a binary heap where poll() always returns the smallest element by natural order or by a Comparator, such as Comparator.comparingInt(Task::priority). Insert and poll are O(log n) and peek is O(1). For multiple threads use PriorityBlockingQueue. Iterating a PriorityQueue does not give sorted order; only repeated poll() does.
03
An API calls three independent downstream services one after another and takes 900 ms. How would you speed it up?
Since the calls are independent, run them in parallel with CompletableFuture.supplyAsync on a dedicated executor or with virtual threads, then join with allOf. Total latency becomes roughly the slowest call, about 300 ms. Add a timeout per call with orTimeout and a fallback for failures so one slow service does not block the whole response. Structured concurrency is another option in newer Java.
04
Users get LazyInitializationException when the API returns an entity. What is happening?
The entity was loaded inside a transaction, the session closed, and then Jackson touched a lazy association outside it. Do not fix it by turning on open-session-in-view or making everything eager. Instead, map the entity to a DTO inside the service transaction and fetch needed associations explicitly with JOIN FETCH or an entity graph. Spring Boot logs a warning because open-in-view is on by default.
05
Your service throws OutOfMemoryError: Java heap space in production. How do you investigate?
First capture evidence: enable -XX:+HeapDumpOnOutOfMemoryError and check GC logs to see if heap grows steadily, which signals a leak, or spikes, which signals a large request. Analyse the heap dump in Eclipse MAT or VisualVM and look at the dominator tree for big retainers like static maps or caches. Fix the leak or bound the cache, then increase -Xmx only if the real workload needs it.
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).
Declare the class final, make all fields private and final, set them only in the constructor, and provide no setters. For mutable fields like a List or Date, make defensive copies in the constructor and in getters, or use List.copyOf. Immutable objects are thread safe and make good map keys. Java records give a concise way to create shallowly immutable data classes.
08
How do you take a thread dump and a heap dump of a running Java process?
Find the process id with jps or ps, then use jcmd, which is the recommended tool.
jps -l
jcmd <pid> Thread.print > threads.txt
jcmd <pid> GC.heap_dump /tmp/heap.hprof
Older tools jstack and jmap do the same. Take three thread dumps a few seconds apart to spot stuck threads, and analyse heap dumps in Eclipse MAT.
At startup Spring Boot reads auto-configuration classes listed in META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports. Each class uses conditions like @ConditionalOnClass, @ConditionalOnMissingBean and @ConditionalOnProperty, so it creates beans only when the library is on the classpath and you have not defined your own. Run with --debug to see the condition report showing what was applied and why.
10
Your REST API returns stack traces to clients when errors happen. How do you design proper error handling?
Never expose stack traces; they leak internals. In Spring Boot use a @RestControllerAdvice with @ExceptionHandler methods that map domain exceptions to status codes, such as 404 for not found and 400 for validation. Return a consistent body, ideally RFC 7807 ProblemDetail, with a code, message and trace id. Log full details on the server with the same trace id.
11
What is garbage collection and how does the JVM decide an object is garbage?
Garbage collection automatically frees memory used by objects that are no longer reachable. The JVM starts from GC roots such as local variables on thread stacks, static fields and active threads, and marks every object reachable from them. Anything not marked is garbage. Because reachability is used rather than reference counting, circular references between unreachable objects are still collected.
12
What is the difference between lazy and eager loading?
Lazy loading fetches an association only when it is first accessed, using a proxy; eager loading fetches it immediately with the parent. In JPA, @ManyToOne and @OneToOne default to EAGER, while @OneToMany and @ManyToMany default to LAZY. Best practice is to make all associations lazy and fetch what each use case needs with JOIN FETCH or entity graphs, which avoids loading huge object graphs.
13
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.
14
Configure a Resilience4j circuit breaker on a client call in Spring Boot.
HashMap stores entries in an array of buckets. It computes the key's hashCode(), spreads the bits and picks a bucket index. Collisions are stored as a linked list in the bucket, and since Java 8 a bucket with more than 8 entries (when the table has at least 64 buckets) becomes a red-black tree, making the worst case O(log n). When size passes capacity times load factor 0.75, it resizes to double.
The simplest safe options are an enum or the holder idiom.
public class Config {
private Config() {}
private static class Holder {
static final Config INSTANCE = new Config();
}
public static Config getInstance() {
return Holder.INSTANCE;
}
}
The JVM loads Holder lazily and class initialisation is thread safe. An enum singleton also resists reflection and serialization attacks.
17
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.
18
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.
19
An API needs to find the price band for any amount, for example the nearest lower slab. Which structure fits?
TreeMap is ideal because it keeps keys sorted and offers navigation methods. Store slab start amounts as keys and the band as value, then floorEntry(amount) returns the largest slab not above the amount in O(log n). ceilingKey, headMap and tailMap help with similar range queries such as tax slabs or delivery charges.
20
Memory usage is high because millions of Integer objects are stored in an ArrayList. What would you do?
Each Integer is a separate object with header overhead and a reference, so a List of Integer uses several times more memory than the raw data. If size is known, use an int[] array. Otherwise use primitive collections from libraries such as Eclipse Collections or fastutil, which store ints directly. This also improves cache performance and reduces GC pressure.
First check why tasks are slow, since slow tasks fill pools. Then choose a policy: a bounded queue with CallerRunsPolicy applies backpressure by running the task in the submitting thread; otherwise return a fast 503 so clients retry. Tune pool and queue sizes from load tests. Never use an unbounded queue, because it hides the problem until memory runs out.
23
GC pauses of two seconds are causing request timeouts. How would you reduce them?
Turn on GC logging with -Xlog:gc* and confirm which collections cause the pauses. Reduce allocation rate by fixing heavy object creation in hot paths. Size the heap correctly and set -Xms equal to -Xmx to avoid resizing. Tune G1 with MaxGCPauseMillis or move to ZGC for sub-millisecond pauses on large heaps. Retest under load before rolling out.
24
Your application hangs and CPU is near zero. How do you find out why?
Low CPU with a hang suggests threads are blocked, often a deadlock or waiting on a slow resource. Take several thread dumps with jcmd pid Thread.print. The JVM reports detected deadlocks at the end of the dump. Otherwise look for many threads BLOCKED on the same lock or WAITING on a connection pool or socket read, then fix lock order, add timeouts or increase the pool.
25
How do you explain OOP concepts to a junior developer who is new to Java?
Situation: I mentored two interns who struggled with OOP. Task: help them design classes for a library app. Action: I used real objects they knew, like Book and Member, showed encapsulation with private fields, then wrote one interface with two implementations to show polymorphism, and reviewed their code daily. Result: within two weeks they designed modules on their own and their pull requests needed fewer review comments.
26
Two users booking the last seat both succeed. How do you prevent double booking?
This is a race between read and write. Use a database guarantee: a unique constraint on seat and show, an atomic conditional update like UPDATE seats SET status = 'BOOKED' WHERE id = ? AND status = 'FREE' and check the affected row count, or pessimistic locking with SELECT FOR UPDATE. Optimistic locking with a version column also works, retrying or failing the loser.
27
Your Spring Boot service takes 40 seconds to start in Kubernetes and pods get killed. How do you fix it?
First set a startupProbe so Kubernetes waits for startup before liveness checks begin. Then reduce start time: remove unused starters, enable lazy initialisation where safe, avoid heavy work in @PostConstruct, give enough CPU at start and consider AppCDS. For very fast startup, a GraalVM native image built with Spring AOT can start in under a second, with some trade-offs.
28
A file handle leak causes Too many open files errors after a day. What is the likely cause?
Streams, readers or connections are opened but not closed on all paths, especially when an exception is thrown before close(). Check with lsof or jcmd which files are open. Fix by wrapping every resource in try-with-resources so it always closes, and make sure Files.lines() and Files.list() streams are closed too, since they hold file handles.
29
Implement the Builder pattern for a User class with many optional fields.
A builder avoids long constructors.
public class User {
private final String name; private final int age;
private User(Builder b) { name = b.name; age = b.age; }
public static class Builder {
private String name; private int age;
public Builder name(String n) { name = n; return this; }
public Builder age(int a) { age = a; return this; }
public User build() { return new User(this); }
}
}
Usage: new User.Builder().name("Asha").age(25).build(). Lombok @Builder generates this.
30
Should a service layer throw checked or unchecked exceptions? Defend your choice.
I prefer unchecked domain exceptions in the service layer. Checked exceptions force every caller to catch or declare them, leak low level details through layers and do not work well with lambdas. Unchecked exceptions with clear names, handled centrally by a controller advice, keep code clean. Spring follows the same idea by translating SQLException into its unchecked DataAccessException family.
Tips to crack the Zoho Java interview
Practise C programming output and pointer questions, which commonly appear in Zoho's written test.
Prepare for advanced programming rounds where you build a small application, such as a booking system, without external libraries.
Learn about Zoho's privacy-focused, in-house product approach and its rural offices in places like Tenkasi.
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; Zoho interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the Zoho Java interview?
Candidates usually go through 5 stages: Written test (aptitude + C programming output); Basic programming round; Advanced programming round; 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 Zoho Java interview?
This practice set leans on JDBC, Hibernate and JPA (5), Collections Framework (5), Java Basics and JVM (5), OOP in Java (5). Revise those first, then practise explaining one or two of your own projects end to end, because most Zoho interviewers ask you to walk through real work.
Are these the exact questions asked at Zoho?
No. These are curated practice questions that match the skills and difficulty usually tested in product interviews like Zoho's. They are not a leaked or verified list of past questions.
Where does Zoho hire Java professionals in India?
Zoho has large teams in Chennai, Tenkasi. Openings and locations change often, so check the Zoho careers page and filter by city and experience.