Here you get a free Java Interview Question which helps you to Give Correct Answer of the Question in the Interview. It also helps you for you college exams Preparation.
Core Java
- Explain the difference between
final
,finally
, andfinalize
in Java. - How does the
String
class achieve immutability? - Discuss how garbage collection works in Java and its limitations.
- What is the difference between
StringBuilder
andStringBuffer
? - Can you override the
equals()
andhashCode()
methods? Why is it important to do so correctly? - Explain the
transient
andvolatile
keywords with examples. - How does autoboxing and unboxing work in Java? Provide examples.
- Discuss the significance of
Serializable
interface and its impact on Java objects. - What are method references in Java? Provide an example.
- What is the purpose of the
native
keyword in Java?
Object-Oriented Programming
- How does Java handle multiple inheritance problems?
- Explain the principle of polymorphism with a code example.
- What is the Liskov Substitution Principle (LSP)? How does Java implement it?
- Discuss the significance of
super
andthis
keywords in Java. - Explain the role of abstraction and interfaces in Java.
- How is encapsulation enforced in Java? Provide a practical example.
- What is the difference between method overloading and method overriding?
- Can you explain dynamic method dispatch in Java with an example?
- What are covariant return types? Provide an example.
- How do Java inner classes support OOP principles?
Collection Frameworks
- What is the difference between
HashMap
,TreeMap
, andLinkedHashMap
? - Explain the working of
HashSet
and how it prevents duplicate entries. - What is the difference between
ArrayList
andLinkedList
? - How do you implement a custom comparator in Java?
- Discuss the internal working of
ConcurrentHashMap
. - Explain the difference between
fail-fast
andfail-safe
iterators. - How does the
CopyOnWriteArrayList
differ from a normalArrayList
? - What is the significance of
EnumSet
andEnumMap
? - Explain the
PriorityQueue
and how it differs from other queues. - How does
java.util.stream
interact with the collections framework?
Multithreading and Concurrency
- What are the differences between
synchronized
andReentrantLock
? - How does the
volatile
keyword affect thread safety? - What is the difference between
Thread
andRunnable
interfaces? - Explain the concept of thread pool and how it is implemented in Java.
- How does the
Callable
interface differ fromRunnable
? - What are the benefits of using the
Fork/Join
framework? - How does the
CompletableFuture
API work in Java? - Discuss the role of
CountDownLatch
andCyclicBarrier
. - What is the difference between
Semaphore
andLock
in Java? - Explain the significance of the
ThreadLocal
class.
Exception Handling
- How does Java differentiate between checked and unchecked exceptions?
- Can a
try
block have multiplecatch
blocks? Provide an example. - What is the purpose of a
finally
block? Can it override areturn
statement? - Explain the difference between
throw
andthrows
keywords. - How do you create custom exceptions in Java?
- Can you catch multiple exceptions in one
catch
block? Provide an example. - Discuss how suppressed exceptions are handled in Java.
- Explain the purpose of the
Error
class and how it differs fromException
. - Can exceptions be rethrown? Provide an example.
- What is the
try-with-resources
statement, and how does it enhance exception handling?
Java 8 Features
- How do lambda expressions improve code readability?
- Explain the working of the
Optional
class in Java 8. - What are streams, and how do they differ from collections?
- How does the
filter()
operation in streams work? - Explain the concept of functional interfaces with examples.
- What is the difference between intermediate and terminal operations in streams?
- How does the
Collectors
utility class work in streams? - What is the significance of default methods in interfaces?
- How does
java.time
API improve date and time handling? - Discuss the working of
forEach()
in Java 8 streams.
File I/O and NIO
- What is the difference between
FileReader
andBufferedReader
? - How does Java NIO differ from traditional I/O?
- Explain the role of
Path
andPaths
in Java NIO. - What are the key features of the
Files
class in NIO? - How do you read and write binary data in Java?
- Discuss the concept of file channels in Java.
- How does the
WatchService
API work for monitoring file changes? - Explain how memory-mapped files are used in Java.
- How do you handle character encoding in Java file operations?
- What is the purpose of the
RandomAccessFile
class?
JDBC (Java Database Connectivity)
- What are the key steps to establish a JDBC connection?
- How does
PreparedStatement
differ fromStatement
in JDBC? - What is the purpose of batch processing in JDBC?
- Explain the role of the
ResultSet
interface in database operations. - How does transaction management work in JDBC?
- What are savepoints, and how are they used in JDBC?
- How do you handle SQL exceptions effectively in Java?
- Discuss the use of connection pooling in JDBC.
- What is the significance of metadata in JDBC?
- How does the
CallableStatement
handle stored procedures?
Design Patterns in Java
- Explain the Singleton pattern and how it is implemented in Java.
- How does the Factory Method pattern differ from the Abstract Factory pattern?
- Discuss the Builder pattern with a practical example.
- What is the Decorator pattern, and how does Java support it?
- Explain the concept of the Proxy pattern with examples.
- How is the Observer pattern implemented in Java?
- What is the Strategy pattern? Provide a code example.
- How does the Adapter pattern help with compatibility issues?
- Discuss the role of Dependency Injection and how it relates to Java design patterns.
- What are microservices-related design patterns in Java?
Java Memory Management
- What is the structure of the Java memory model?
- How does the Java Virtual Machine (JVM) handle memory allocation?
- Discuss the different garbage collection algorithms in Java.
- How does the JVM manage the heap and stack memory?
- What is the role of the
Metaspace
in Java 8? - How does Java detect and handle memory leaks?
- Explain the use of
SoftReference
,WeakReference
, andPhantomReference
. - What is the difference between minor GC and major GC?
- How does the
-Xms
and-Xmx
options affect JVM performance? - What are the tools available for profiling memory usage in Java?
Advanced Topics
- What is reflection in Java, and how is it used?
- How does the Java ClassLoader work?
- Explain the concept of dynamic proxies in Java.
- What is the role of annotations in Java?
- How does the
java.lang.instrument
package support bytecode manipulation? - What are generics in Java, and how do they enforce type safety?
- Explain type erasure and its impact on generics.
- How does Java achieve backward compatibility?
- Discuss how modules were introduced in Java 9.
- What is the purpose of the
SecurityManager
class?