Java Interview Questions and Answers

Top 100 JAVA Interview Questions for Freshers

Java is one of the most widely used programming languages in top tech companies, including IDM TechPark. Its platform independence, robustness, and extensive libraries make it an essential skill for developers. To secure a Java developer role at IDM TechPark, candidates must be well-versed in Java concepts and ready to tackle both the Java Online Assessment and Technical Interview Round.

To help you succeed, we have compiled a list of the Top 100 Java Interview Questions along with their answers. Mastering these will give you a strong edge in cracking Java interviews at IDM TechPark.

1. What is Java?

Answer: Java is a high-level, object-oriented programming language developed by Sun Microsystems (now owned by Oracle). It is platform-independent due to its "Write Once, Run Anywhere" (WORA) capability, enabled by the Java Virtual Machine (JVM).

2. What are the main features of Java?

Answer: Key features of Java include:

Platform independence (via JVM)
Object-oriented (supports concepts like inheritance, polymorphism, encapsulation, and abstraction)
Automatic memory management (Garbage Collection)
Multithreading support
Security (via bytecode verification)

3. What is the difference between JDK, JRE, and JVM?

Answer:

JDK (Java Development Kit): Includes tools to develop, compile, and run Java programs (JRE + compiler + debugger, etc.).
JRE (Java Runtime Environment): Provides runtime libraries and environment to run Java applications (JVM + core libraries).
JVM (Java Virtual Machine): Converts Java bytecode into machine code and runs it on different operating systems.

4. What are primitive data types in Java?

Answer: Java has 8 primitive data types:

Integer types: byte, short, int, long
Floating-point types: float, double
Character type: char
Boolean type: boolean

5. What is the difference between "==" and .equals() in Java?

Answer:

== checks reference equality (whether two references point to the same object).
.equals() checks content equality (whether two objects have the same value, overridden in classes like String).

6. What is an object in Java?

Answer: An object is an instance of a class that has state (fields/attributes) and behavior (methods).

7. What is the difference between ArrayList and LinkedList?

Answer:

FeatureArrayListLinkedList

StorageDynamic arrayDoubly linked list

Insertion/DeletionSlow (shifting elements)Fast (relinking nodes)

Access speedFast (O(1) for index access)Slow (O(n) traversal)

8. What is a constructor in Java?

Answer: A constructor is a special method that initializes an object when it is created. It has the same name as the class and does not have a return type.

Example:

class Car { String model; Car(String m) { model = m; } }

9. What is method overloading and method overriding?

Answer:

Method Overloading: Multiple methods in the same class with the same name but different parameters.
Method Overriding: A subclass provides a specific implementation of a method from its superclass.

10. What is the difference between static and final keywords?

Answer:

static: Belongs to the class, not the object (shared by all instances).
final: Used to declare constants, prevent method overriding, and prevent inheritance.

11. What are access modifiers in Java?

Answer:
Access modifiers define the scope of variables, methods, and classes:

public: Accessible everywhere
protected: Accessible in the same package and subclasses
default (no modifier): Accessible only in the same package
private: Accessible only within the same class

12. What is inheritance in Java?

Answer:
Inheritance allows a class to inherit fields and methods from another class using the extends keyword. It promotes code reuse.

13. What is polymorphism?

Answer:
Polymorphism allows an object to take many forms:

Compile-time (method overloading)
Runtime (method overriding)

14. What is method overriding?

Answer:
When a subclass provides a specific implementation of a method already defined in its superclass.

15. What is abstraction in Java?

Answer:
Abstraction hides internal details and shows only functionality. It’s achieved using abstract classes and interfaces.

16. What is encapsulation?

Answer:
Encapsulation is the bundling of data and methods in a single unit (class). Fields are usually private with public getters/setters.

Q17. What is inheritance in Java?
Answer:

Inheritance is a feature in Java where one class (called the subclass or child class) inherits properties and behaviors (fields and methods) from another class (called the superclass or parent class). It promotes code reusability and supports method overriding, enabling polymorphism.

18. What is the difference between abstract class and interface?

Answer:

Abstract ClassInterface

Can have method bodyCannot have method body (except default/static)

Can have constructorsCannot have constructors

Supports partial abstractionSupports full abstraction

19. What is the difference between Array and ArrayList?

Answer:

Array: Fixed size, supports both primitives and objects
ArrayList: Dynamic size, supports only objects, part of java.util package

20. What is the use of the final keyword?

Answer:

final class: Cannot be extended
final method: Cannot be overridden
final variable: Cannot be reassigned

21. What is the purpose of the this keyword in Java?
The this keyword refers to the current instance of the class. It is used to distinguish between instance variables and parameters when they have the same name.

22. What are Java wrapper classes?
Wrapper classes are used to convert primitive data types into objects. Common wrapper classes include Integer, Double, Float, Character, and Boolean.

23. What is method overloading in Java?
Method overloading means defining multiple methods with the same name but different parameters (type or number) within the same class. It helps achieve compile-time polymorphism.

24. What is the difference between == and .equals() in Java?

== checks if two references point to the same memory location.
.equals() checks if two objects have the same content or value.

25. What is a constructor in Java?
A constructor is a special method used to initialize objects. It has the same name as the class and no return type. It is automatically called when an object is created.

1. What is the difference between an interface and an abstract class?

An interface only contains method declarations (without implementation), whereas an abstract class can have both abstract methods and concrete methods. A class can implement multiple interfaces but can extend only one abstract class.

2. What are wrapper classes in Java?

Wrapper classes are used to convert primitive data types into objects. For example, Integer is the wrapper class for int, Double for double, and so on. These are part of Java’s object-oriented nature and are used in collections and generics.

3. What is the super keyword in Java?

The super keyword is used to refer to the immediate parent class. It can be used to call the parent class constructor, access parent class methods, or refer to parent class variables when they are overridden in the child class.

4. What is a static block?

A static block is a block of code inside a class that is executed once when the class is loaded into memory. It is typically used for static variable initialization. Example:

class Test { static { System.out.println("Static block executed"); } }

5. What is a singleton class?

A singleton class ensures that only one instance of the class is created during the runtime of the application. This is achieved by making the constructor private and providing a static method to get the single instance.

6. How does Java handle exceptions?

Java provides a robust mechanism for exception handling using try, catch, finally, throw, and throws. try is used to define a block of code where exceptions may occur, catch handles the exception, finally executes code regardless of exception occurrence, throw is used to throw exceptions, and throws declares exceptions that may be thrown by a method.

7. What is multithreading in Java?

Multithreading allows concurrent execution of multiple threads, which improves the efficiency of a program. Threads can be created by extending the Thread class or implementing the Runnable interface. Java provides synchronization to handle concurrent access to shared resources.

8. What is the difference between String, StringBuffer, and StringBuilder?

String is immutable, meaning every modification creates a new object. StringBuffer is mutable and thread-safe, making it useful for multithreading. StringBuilder is also mutable but is not synchronized, making it faster than StringBuffer.

9. What is the volatile keyword?

The volatile keyword ensures that changes made to a variable by one thread are immediately visible to all other threads. It prevents thread caching and guarantees that the variable is always read from main memory.

10. What is the difference between HashMap and Hashtable?

HashMap is not synchronized and allows null keys and values, making it faster but not thread-safe. Hashtable is synchronized, meaning it is thread-safe but slower. ConcurrentHashMap is preferred for thread-safe operations in modern applications.

11. What is method reference in Java?

Method reference is a shorthand notation for lambda expressions. It allows you to refer to methods directly using ClassName::methodName. Example:

List<String> names = Arrays.asList("John", "Doe"); names.forEach(System.out::println);

12. What is a functional interface?

A functional interface is an interface that contains exactly one abstract method. It can have multiple default or static methods. It is used in lambda expressions and method references. Example:

@FunctionalInterface interface MyInterface { void show(); }

13. What is a default method in an interface?

A default method in an interface has a body and allows interfaces to have implemented methods without breaking existing classes. It is defined using the default keyword inside an interface.

14. What is the difference between checked and unchecked exceptions?

Checked exceptions are checked at compile-time and must be handled using try-catch or throws. Examples include IOException and SQLException. Unchecked exceptions occur at runtime and are subclasses of RuntimeException, like NullPointerException and ArithmeticException.

15. What is reflection in Java?

Reflection is a feature in Java that allows us to inspect and modify classes, methods, and fields at runtime. It is used in frameworks, testing tools, and serialization. Example:

Class<?> cls = Class.forName("MyClass"); Method[] methods = cls.getDeclaredMethods();

16. What is garbage collection in Java?

Garbage collection is the process of automatically reclaiming memory occupied by unused objects. Java’s garbage collector removes objects that are no longer reachable to free up memory. The System.gc() method suggests garbage collection but does not guarantee it.

17. What is a lambda expression?

A lambda expression is a concise way to write an anonymous function. It helps reduce boilerplate code in functional programming. Example:

(x, y) -> x + y;

18. What is the difference between Comparator and Comparable?

Comparable is used for natural ordering of objects and requires the class to implement the compareTo method. Comparator is used for custom sorting and requires implementing the compare method in a separate class.

19. What is constructor chaining?

Constructor chaining is the process of calling one constructor from another in the same class or parent class using this() or super(). It helps avoid redundant code.

20. What is the Java Stream API?

The Java Stream API provides a functional approach to process collections of data using operations like map(), filter(), and reduce(). It is useful for working with large data sets efficiently. Example:

List<String> names = List.of("Alice", "Bob", "Charlie"); names.stream().filter(name -> name.startsWith("A")).forEach(System.out::println)

21. What is the difference between ArrayList and LinkedList in Java?

ArrayList uses a dynamic array to store elements and allows fast random access.
LinkedList uses a doubly-linked list and is more efficient for insertions and deletions, especially in the middle of the list.

22. What is synchronization in Java and why is it important?
Synchronization is used to control access to shared resources in multithreaded environments. It ensures that only one thread can access a synchronized block or method at a time, preventing race conditions and ensuring thread safety.

23. Difference between throw and throws keywords in Java?

**throw** is used to actually throw an exception.
**throws** is used in a method signature to declare which exceptions might be thrown.

Example:

void myMethod() throws IOException { throw new IOException("File not found"); }

24. What are inner classes in Java?
Inner classes are classes defined within another class. Types include:

Non-static inner class (also called member inner class)
Static nested class
Local inner class (defined inside a method)
Anonymous inner class (used for short implementation, especially in event handling)

25. What is the final keyword used for in Java?
The final keyword has three uses:

Final variable – value cannot be changed once assigned.
Final method – cannot be overridden by subclasses.
Final class – cannot be extended by any other class.

1. How do you implement a thread-safe singleton class in Java?

Use double-checked locking with volatile:

class Singleton { private static volatile Singleton instance; private Singleton() {} public static Singleton getInstance() { if (instance == null) { synchronized (Singleton.class) { if (instance == null) { instance = new Singleton(); } } } return instance; } }

2. How do you implement a deadlock in Java?

class DeadlockExample { static final Object lock1 = new Object(); static final Object lock2 = new Object(); public static void main(String[] args) { new Thread(() -> { synchronized (lock1) { synchronized (lock2) { System.out.println("Thread 1"); } } }).start(); new Thread(() -> { synchronized (lock2) { synchronized (lock1) { System.out.println("Thread 2"); } } }).start(); } }

Deadlock happens when Thread 1 locks lock1 and waits for lock2, while Thread 2 locks lock2 and waits for lock1.

3. How do you avoid deadlocks in Java?

Always acquire locks in a consistent order.
Use timeouts when acquiring locks.
Minimize lock duration.

4. How do you implement a producer-consumer problem in Java?

Using BlockingQueue:

class ProducerConsumer { public static void main(String[] args) { BlockingQueue<Integer> queue = new LinkedBlockingQueue<>(5); new Thread(() -> { try { queue.put(1); } catch (InterruptedException e) {} }).start(); new Thread(() -> { try { queue.take(); } catch (InterruptedException e) {} }).start(); } }

put() waits if the queue is full, and take() waits if empty.

5. What is the difference between Callable and Runnable?

Runnable does not return a value, while Callable<T> returns a result and can throw exceptions.

Callable<Integer> task = () -> 42; ExecutorService executor = Executors.newFixedThreadPool(1); Future<Integer> future = executor.submit(task); System.out.println(future.get()); // 42

6. How do you implement a custom exception in Java?

class CustomException extends Exception { public CustomException(String message) { super(message); } }

7. How do you use Java 8 Streams to find the second-highest number in a list?

List<Integer> list = List.of(5, 1, 9, 7); int secondHighest = list.stream().sorted(Comparator.reverseOrder()).skip(1).findFirst().orElse(-1);

8. How do you detect a cycle in a linked list?

Use Floyd’s Cycle Detection Algorithm (Tortoise and Hare):

boolean hasCycle(Node head) { Node slow = head, fast = head; while (fast != null && fast.next != null) { slow = slow.next; fast = fast.next.next; if (slow == fast) return true; } return false; }

9. How do you implement LRU Cache in Java?

Using LinkedHashMap:

class LRUCache<K, V> extends LinkedHashMap<K, V> { private final int capacity; LRUCache(int capacity) { super(capacity, 0.75f, true); this.capacity = capacity; } @Override protected boolean removeEldestEntry(Map.Entry<K, V> eldest) { return size() > capacity; } }

10. How do you convert a binary tree to a doubly linked list?

class TreeNode { int val; TreeNode left, right; } TreeNode head, prev; void convert(TreeNode root) { if (root == null) return; convert(root.left); if (prev == null) head = root; else { prev.right = root; root.left = prev; } prev = root; convert(root.right); }

11. How do you reverse a linked list in Java?

Node reverse(Node head) { Node prev = null, curr = head; while (curr != null) { Node next = curr.next; curr.next = prev; prev = curr; curr = next; } return prev; }

12. How do you implement quicksort in Java?

void quicksort(int[] arr, int low, int high) { if (low < high) { int pi = partition(arr, low, high); quicksort(arr, low, pi - 1); quicksort(arr, pi + 1, high); } } int partition(int[] arr, int low, int high) { int pivot = arr[high], i = low; for (int j = low; j < high; j++) { if (arr[j] < pivot) { swap(arr, i++, j); } } swap(arr, i, high); return i; }

13. How do you merge two sorted linked lists?

Node merge(Node l1, Node l2) { if (l1 == null) return l2; if (l2 == null) return l1; if (l1.val < l2.val) { l1.next = merge(l1.next, l2); return l1; } else { l2.next = merge(l1, l2.next); return l2; } }

14. How do you count the occurrences of each word in a file using Java 8 Streams?

Map<String, Long> wordCount = Files.lines(Path.of("file.txt")) .flatMap(line -> Arrays.stream(line.split("\\s+"))) .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

15. How do you remove duplicate characters from a string?

String removeDuplicates(String str) { return str.chars().distinct().mapToObj(c -> String.valueOf((char) c)).collect(Collectors.joining()); }

16. How do you find the longest substring without repeating characters?

int longestUniqueSubstring(String s) { Map<Character, Integer> map = new HashMap<>(); int maxLen = 0, left = 0; for (int right = 0; right < s.length(); right++) { if (map.containsKey(s.charAt(right))) left = Math.max(left, map.get(s.charAt(right)) + 1); map.put(s.charAt(right), right); maxLen = Math.max(maxLen, right - left + 1); } return maxLen; }

17. How do you execute a method at a fixed interval in Java?

ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1); scheduler.scheduleAtFixedRate(() -> System.out.println("Task"), 0, 1, TimeUnit.SECONDS);

18. How do you implement a binary search?

int binarySearch(int[] arr, int target) { int left = 0, right = arr.length - 1; while (left <= right) { int mid = left + (right - left) / 2; if (arr[mid] == target) return mid; if (arr[mid] < target) left = mid + 1; else right = mid - 1; } return -1; }

19. How do you create an immutable class in Java?

Declare class as final.
Make fields private final.
Provide no setters, only getters.

20. How do you implement a thread pool in Java?

ExecutorService pool = Executors.newFixedThreadPool(5); pool.execute(() -> System.out.println("Task executed"));

Sure! Here are advanced Java interview questions and answers (21–25) in a clear text format:

21. What is the Java Memory Model (JMM)?

The Java Memory Model defines how threads interact through memory and what behaviors are allowed in concurrent execution. It ensures visibility, atomicity, and ordering of variables accessed by multiple threads. Key concepts include:

Volatile variables: Ensure visibility of changes to variables across threads.
Happens-before relationship: Determines memory visibility and synchronization guarantees.
Synchronized blocks: Provide mutual exclusion and establish happens-before relationships.

22. What are functional interfaces and how are they used in Java 8+?

A functional interface is an interface with exactly one abstract method. They are used primarily with lambda expressions and method references.

Examples:

Runnable, Callable, Comparable, Function<T, R>, Predicate<T>

Custom example:

@FunctionalInterface interface MyFunction { int operate(int a, int b); }

Used like:

MyFunction add = (a, b) -> a + b;

23. Explain the difference between HashMap, LinkedHashMap, and TreeMap.

FeatureHashMapLinkedHashMapTreeMap

OrderNo orderInsertion orderSorted by keys

PerformanceFastSlightly slowerSlower (Red-Black Tree)

Null keys/values1 null key, multiple null valuesSame as HashMapNo null keys

24. What is the difference between final, finally, and finalize()?

final: Keyword to declare constants, prevent inheritance/overriding.
finally: Block used with try-catch to execute code regardless of exceptions.
finalize(): A method called by the GC before reclaiming memory. (Deprecated in Java 9+)

Example:

final int MAX = 100; try { // code } finally { // clean-up code } @Override protected void finalize() throws Throwable { // resource release }

25. How does Java achieve platform independence and what is the role of JVM?

Java achieves platform independence through the use of bytecode, which is generated by the Java compiler and can run on any system with a compatible Java Virtual Machine (JVM).

JVM: Executes bytecode, handles memory, manages threads, performs garbage collection, and ensures security.
This architecture follows:
Java Source Code → Bytecode (.class files) → JVM → Machine Code

1. What are SOLID principles in Java?

SOLID stands for:

S: Single Responsibility Principle (Class should have one responsibility)
O: Open/Closed Principle (Open for extension, closed for modification)
L: Liskov Substitution Principle (Subclasses should replace parent classes)
I: Interface Segregation Principle (No unnecessary methods in interfaces)
D: Dependency Inversion Principle (Depend on abstractions, not concretions)

2. What is a design pattern? Name three commonly used patterns.

A design pattern is a best practice solution for recurring software design problems.

Singleton (Ensures a single instance of a class)
Factory (Creates objects without exposing instantiation logic)
Observer (One-to-many dependency where a change in one object notifies all observers)

3. What is the difference between Stack and Heap memory?

Stack: Stores method calls, local variables, follows LIFO (Last In, First Out).
Heap: Stores objects dynamically allocated, managed by Garbage Collector.

4. How does Java handle memory management?

Java uses Garbage Collection (GC) to automatically deallocate unused objects. The GC runs in different phases (Mark, Sweep, Compact) to free memory.

5. Explain the differences between ArrayList and LinkedList.

ArrayList: Fast random access (O(1)), slow insert/delete (O(n)).
LinkedList: Slow random access (O(n)), fast insert/delete (O(1)).

6. What is the difference between HashMap and ConcurrentHashMap?

HashMap is not thread-safe and allows null keys/values.
ConcurrentHashMap is thread-safe, using segment-level locks to avoid blocking threads.

7. How does a HashMap work internally in Java?

Uses an array of buckets.
Computes a hash code for keys and stores entries in buckets.
Uses Linked List or Tree (Java 8+) to handle collisions.
Uses rehashing when load factor > 0.75.

8. How do you detect a cycle in a linked list?

Use Floyd’s Cycle Detection Algorithm (Tortoise and Hare):

boolean hasCycle(Node head) { Node slow = head, fast = head; while (fast != null && fast.next != null) { slow = slow.next; fast = fast.next.next; if (slow == fast) return true; } return false; }

9. How do you implement a thread-safe singleton class in Java?

10. How does Java achieve multithreading?

Java achieves multithreading using:

Thread class (extends Thread)
Runnable interface (implements Runnable)
ExecutorService (ThreadPool)

11. What is the difference between synchronized and volatile?

synchronized: Prevents multiple threads from accessing a block of code.
volatile: Ensures that a variable is always read from main memory, preventing caching issues.

12. How do you implement LRU Cache in Java?

Using LinkedHashMap:

13. What is the difference between NoSQL and SQL databases?

FeatureSQL (Relational)NoSQL (Non-relational)

StructureTables & SchemaDocuments, Key-Value, Graph

ScalabilityVerticalHorizontal

TransactionsACIDBASE (Eventually Consistent)

ExamplesMySQL, PostgreSQLMongoDB, Redis

14. What is an index in SQL?

An index improves query performance by enabling faster searches. Example:

CREATE INDEX idx_name ON employees (name);

15. What is normalization in SQL?

Normalization reduces redundancy by organizing data into multiple related tables.

1NF: Remove duplicate columns.
2NF: Ensure all attributes depend on the primary key.
3NF: Remove transitive dependencies.

16. How do you prevent SQL injection?

Use Prepared Statements:

PreparedStatement stmt = conn.prepareStatement("SELECT * FROM users WHERE email = ?"); stmt.setString(1, email); ResultSet rs = stmt.executeQuery();

17. What happens when you type a URL in a browser and press Enter?

DNS lookup: Resolves domain to an IP address.
TCP handshake: Establishes a connection (SYN, SYN-ACK, ACK).
HTTP request: Browser sends GET/POST request.
Server response: Sends HTML, CSS, JS files.
Rendering: Browser parses and displays content.

18. How does load balancing work?

Distributes traffic across multiple servers to improve reliability and performance. Common algorithms:

Round-robin
Least connections
IP Hashing

19. What is CAP theorem in distributed systems?

CAP theorem states that a distributed system cannot have all three:

Consistency (Every read gets the latest write)
Availability (System is always available)
Partition Tolerance (System works despite network failures)

Examples:

CA: Relational Databases
AP: NoSQL (Cassandra)
CP: MongoDB

20. How do you design a URL Shortener like Bit.ly?

Database: Store long URLs with a unique short code.
Encoding: Use Base62 (abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789).
Caching: Use Redis for faster lookup.
Load Balancer: Handle traffic distribution.
API Design:
- POST /shorten → Shorten URL
- GET /{shortCode} → Redirect to long URL

Example code to generate a short URL:

String base62 = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; String encode(long id) { StringBuilder shortUrl = new StringBuilder(); while (id > 0) { shortUrl.append(base62.charAt((int)(id % 62))); id /= 62; } return shortUrl.reverse().toString(); }

21. What are the different types of class loaders in Java and how do they work?

Java uses class loaders to load classes at runtime. The main types are:

Bootstrap ClassLoader: Loads core Java classes (java.lang.*, etc.) from the JDK.
Extension ClassLoader: Loads classes from the JDK's ext directory.
System/Application ClassLoader: Loads classes from the classpath (e.g., user-defined classes).

Class loaders follow a parent delegation model, where each class loader delegates the loading request to its parent before attempting to load the class itself.

22. Explain the internal implementation of HashMap in Java.

HashMap stores data in an array of Node<K,V> (buckets).
It uses hashCode() and equals() to determine the bucket and resolve collisions.
Collisions are handled using:
- Chaining (linked list or tree in Java 8+).
Java 8 introduced treeification: when the number of entries in a bucket exceeds a threshold (default: 8), the linked list becomes a balanced tree (TreeNode) for faster lookups.

Time complexity (average case):

Get/Put: O(1) (hashing)
Worst case (pre-Java 8): O(n); Post-Java 8: O(log n

23. What is the difference between synchronized and Lock in Java concurrency?

synchronized:
- Implicit monitor lock.
- Automatically released.
- Cannot interrupt a thread waiting to acquire the lock.
- No timeout.
Lock (java.util.concurrent.locks.Lock):
- Explicit control over locking/unlocking.
- Can check if a lock is available (tryLock()).
- Supports interruption and timeout.
- Can implement fair locking (ReentrantLock(true)).

Use Lock when more flexibility and control are required.

24. What is method reference and how does it differ from lambda expressions?

Method reference is a shorthand notation of a lambda expression that calls an existing method.

Syntax:

ClassName::methodName

Example:

List<String> names = Arrays.asList("A", "B", "C"); names.forEach(System.out::println); // method reference // equivalent lambda names.forEach(name -> System.out.println(name));

Difference:

Lambda can contain logic.
Method reference only points to an existing method.

25. How does Garbage Collection (GC) work in Java and what are GC algorithms?

Java GC automatically deallocates memory by removing unreachable objects.

Heap memory structure:

Young Generation (Eden + Survivor)
Old Generation (Tenured)
Metaspace (class metadata in Java 8+)

GC Algorithms:

Serial GC: Single-threaded, suitable for small applications.
Parallel GC: Multi-threaded, high throughput.
CMS (Concurrent Mark-Sweep): Low pause time, deprecated in Java 9.
G1 GC (Garbage First): Default since Java 9, balances pause time and throughput.
ZGC / Shenandoah: Low-latency collectors introduced in later Java versions.

Let me know if you want more questions in the same technical depth or need the content exported!

"Deep Concepts to Elevate Your Career"

This guide provides 100+ Java interview questions along with in-depth concepts to strengthen your expertise.

Download

Java Interview Questions and Answers

Top 100 JAVA Interview Questions for Freshers

"Deep Concepts to Elevate Your Career"

Contact Us

IDM Techpark Erode
1st floor, 33/15 vasavi complex, nalli
hospital road, annamalai layout, near bus
stand, erode 638011

+91-95853-05700

idmtechpark@gmail.com

Software Courses

Full Stack Developer

Java Interview Questions and Answers

Top 100 JAVA Interview Questions for Freshers

"Deep Concepts to Elevate Your Career"

Contact Us

IDM Techpark Erode 1st floor, 33/15 vasavi complex, nalli hospital road, annamalai layout, near bus stand, erode 638011

+91-95853-05700

idmtechpark@gmail.com

Software Courses

Full Stack Developer

IDM Techpark Erode
1st floor, 33/15 vasavi complex, nalli
hospital road, annamalai layout, near bus
stand, erode 638011