Java Interview Questions for 2-3 Years Experience 🚀

By /

Listen to this Post

1️⃣ Core Java

  • Difference between JDK, JRE, and JVM?
    JDK (Java Development Kit) is a software development environment used to develop Java applications. JRE (Java Runtime Environment) provides the libraries and JVM (Java Virtual Machine) to run Java programs. JVM executes Java bytecode.

Code Example:


<h1>Check Java version (JDK)</h1>

java -version
  • Explain OOPs concepts (Encapsulation, Abstraction, Inheritance, Polymorphism).
    Encapsulation: Bundling data with methods. Abstraction: Hiding complex implementation. Inheritance: Deriving new classes from existing ones. Polymorphism: One interface, multiple implementations.

Code Example:

// Polymorphism example
class Animal {
void sound() {
System.out.println("Animal makes a sound");
}
}
class Dog extends Animal {
void sound() {
System.out.println("Dog barks");
}
}

2️⃣ Strings & Collections

  • Why is String immutable in Java?
    Immutability ensures security, thread safety, and efficient memory management.

Code Example:

String str = "Hello";
str.concat(" World"); // Returns new string
System.out.println(str); // Output: Hello
  • Difference between ArrayList and LinkedList?
    ArrayList is resizable array-based, while LinkedList is node-based with pointers.

Code Example:

// ArrayList vs LinkedList
ArrayList<String> arrayList = new ArrayList<>();
LinkedList<String> linkedList = new LinkedList<>();

3️⃣ Exception Handling & Multithreading

  • Difference between Checked and Unchecked Exceptions?
    Checked exceptions are checked at compile-time (e.g., IOException), while unchecked exceptions occur at runtime (e.g., NullPointerException).

Code Example:

try {
int num = Integer.parseInt("abc");
} catch (NumberFormatException e) {
System.out.println("Unchecked Exception: " + e.getMessage());
}

4️⃣ Java 8 Features

  • Explain Lambda Expressions with an example.
    Lambda expressions enable functional programming by providing a clear and concise way to represent methods.

Code Example:

// Lambda example
Runnable r = () -> System.out.println("Lambda running");
new Thread(r).start();

5️⃣ JDBC & Database

  • Difference between Statement and PreparedStatement?
    Statement is used for static SQL, while PreparedStatement is precompiled and used for dynamic SQL.

Code Example:

// PreparedStatement example
String query = "SELECT * FROM users WHERE id = ?";
PreparedStatement ps = connection.prepareStatement(query);
ps.setInt(1, 101);

6️⃣ Spring Boot & Microservices

  • What is Spring Boot, and why is it used?
    Spring Boot simplifies Spring application development with auto-configuration and embedded servers.

Code Example:


<h1>Create a Spring Boot project</h1>

spring init --dependencies=web myproject

What Undercode Say

Java remains a cornerstone in the software development industry, especially for enterprise-level applications. Mastering core Java concepts like OOPs, exception handling, and multithreading is essential for any developer. The of Java 8 features like Lambda Expressions and Streams API has revolutionized how developers write code, making it more concise and functional.

For database interactions, understanding JDBC and the difference between Statement and PreparedStatement is crucial for efficient data handling. Spring Boot has further simplified Java development by reducing boilerplate code and providing robust tools for microservices architecture.

Linux Commands for Java Developers:


<h1>Compile Java file</h1>

javac HelloWorld.java

<h1>Run Java program</h1>

java HelloWorld

<h1>Check Java process</h1>

ps -ef | grep java

<h1>Set Java environment variables</h1>

export JAVA_HOME=/usr/lib/jvm/java-11-openjdk
export PATH=$JAVA_HOME/bin:$PATH

Windows Commands for Java Developers:

[cmd]
:: Compile Java file
javac HelloWorld.java

:: Run Java program
java HelloWorld

:: Check Java version
java -version
[/cmd]

For further reading, visit:

By mastering these concepts and tools, you can confidently tackle Java interviews and build robust applications. Keep practicing and exploring new features to stay ahead in the ever-evolving tech landscape.

References:

initially reported by: https://www.linkedin.com/posts/sumit-yadav-08562422b_java-activity-7300734417910558720-9r02 – Hackers Feeds
Extra Hub:
Undercode AIFeatured Image

Related Posts: