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Java Basics
- Variables (int, float, double, char, boolean, String)
- Data types (Primitive, Non-primitive)
- Operators (Arithmetic, Logical, Relational, Bitwise)
- Conditionals (if, else, else if, switch)
- Loops (for, while, do-while, for-each)
- Methods (static and non-static)
- Arrays and Collections
Object-Oriented Programming (OOP)
- Classes & Objects
- Encapsulation (getters & setters)
- Inheritance
- Polymorphism (method overloading & overriding)
- Abstraction (abstract classes & interfaces)
- Access Modifiers (private, protected, public)
Exception Handling
- Try-Catch Blocks
- Finally Block
- Throws and Throw
- Custom Exceptions
File Handling
- Reading and Writing Files
- BufferedReader and BufferedWriter
- Serialization and Deserialization
Java Collections Framework
- List (ArrayList, LinkedList)
- Set (HashSet, TreeSet)
- Map (HashMap, TreeMap)
- Queue and Deque
- Iterators
Multithreading
- Threads and Runnable Interface
- Synchronized Methods
- Locks
- Executors
Java 8+ Features
- Lambda Expressions (simpler code)
- Streams (data processing)
- Functional Interfaces (Predicate, Consumer, Supplier)
- Default and Static Methods in Interfaces
- Optional Class (handling null)
- Method References
Frameworks and Libraries
- Spring Framework
- Hibernate (ORM)
- Apache Maven and Gradle
- JavaFX (GUI)
Debugging
- System.out.println()
- Debugging in IDEs (breakpoints, stepping through code)
- Loggers (Log4j, SLF4J)
Others
- JVM, JRE, and JDK
- Garbage Collection
- Inner Classes (static and non-static)
- Anonymous Classes
- Recursion
- Java Memory Model
- Annotations
Advanced Topics
- Generics
- Reflection API
- Networking (Sockets, HTTP & HTTPS)
- Regular Expressions
- Dependency Injection
More Learning Material:
- Java Full Stack Roadmap: https://lnkd.in/efwYvfHN
- Java Important Interview Questions: https://lnkd.in/d3a5aN9J
- Spring Roadmap: https://lnkd.in/dk6XiWJm
- Spring Interview Questions: https://lnkd.in/eWBYWMQQ
What Undercode Say:
Java is a versatile and powerful programming language that is widely used in the industry. To excel in Java interviews, it is crucial to have a solid understanding of the core concepts and advanced topics. Here are some commands and codes to practice:
1. Java Basics:
public class Main { public static void main(String[] args) { int a = 10; int b = 20; System.out.println("Sum: " + (a + b)); } }
2. Object-Oriented Programming:
class Animal { void sound() { System.out.println("Animal makes a sound"); } } class Dog extends Animal { void sound() { System.out.println("Dog barks"); } } public class Main { public static void main(String[] args) { Animal myDog = new Dog(); myDog.sound(); } }
3. Exception Handling:
public class Main { public static void main(String[] args) { try { int[] myNumbers = {1, 2, 3}; System.out.println(myNumbers[10]); } catch (Exception e) { System.out.println("Something went wrong."); } } }
4. File Handling:
import java.io.File; import java.io.FileWriter; import java.io.IOException; public class Main { public static void main(String[] args) { try { File myObj = new File("filename.txt"); if (myObj.createNewFile()) { System.out.println("File created: " + myObj.getName()); } else { System.out.println("File already exists."); } } catch (IOException e) { System.out.println("An error occurred."); e.printStackTrace(); } } }
5. Multithreading:
class MyThread extends Thread { public void run() { System.out.println("Thread is running."); } } public class Main { public static void main(String[] args) { MyThread t1 = new MyThread(); t1.start(); } }
6. Java 8+ Features:
import java.util.Arrays; import java.util.List; public class Main { public static void main(String[] args) { List<String> myList = Arrays.asList("a1", "a2", "b1", "c2", "c1"); myList.stream() .filter(s -> s.startsWith("c")) .map(String::toUpperCase) .sorted() .forEach(System.out::println); } }
7. Debugging:
import java.util.logging.Logger; public class Main { private static final Logger logger = Logger.getLogger(Main.class.getName()); public static void main(String[] args) { logger.info("This is an info message"); logger.warning("This is a warning message"); logger.severe("This is a severe message"); } }
8. Advanced Topics:
import java.util.ArrayList; import java.util.List; public class Main { public static void main(String[] args) { List<String> list = new ArrayList<>(); list.add("Java"); list.add("Python"); list.add("C++"); for (String language : list) { System.out.println(language); } } }
For more advanced topics like networking and regular expressions, you can refer to the following resources:
– Java Networking
– Java Regular Expressions
By practicing these codes and commands, you will be well-prepared for your Java interviews. Good luck!
References:
Hackers Feeds, Undercode AI