Question 1

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

Accepted Answer

The JVM (Java Virtual Machine) is the runtime engine that actually executes Java bytecode - it's an abstract machine specification implemented differently on each OS/architecture, and it's what gives Java its 'write once, run anywhere' behavior. The

Question 2

Why is Java considered platform-independent, and what role does bytecode play in this?

Accepted Answer

Java source code is compiled by javac into an intermediate, platform-neutral format called bytecode (.class files), not directly into machine code for a specific CPU/OS. That bytecode is then executed by the JVM, and it's the JVM implementation for e

Question 3

What are the different memory areas allocated by the JVM (heap, stack, method area, PC register, native method stack), and what is stored in each?

Accepted Answer

The JVM divides runtime memory into several distinct areas defined by the JVM specification: (1) Heap - shared across all threads, stores all objects and arrays created with 'new'; it's further divided into Young Generation (Eden + Survivor spaces) a

Question 4

Explain the Java classloader delegation model - how do the Bootstrap, Platform/Extension, and Application classloaders interact, and when would you need a custom classloader?

Accepted Answer

Java classloaders are arranged in a parent-first delegation hierarchy: the Application (System) ClassLoader is a child of the Platform ClassLoader (called the Extension ClassLoader before Java 9), which is a child of the Bootstrap ClassLoader (writte

Question 5

How does the JIT compiler improve performance over pure bytecode interpretation, and what is the difference between the C1 (client) and C2 (server) compilers?

Accepted Answer

The JVM starts out interpreting bytecode line-by-line, which is portable but slow. The JIT (Just-In-Time) compiler improves on this by profiling method execution at runtime and compiling 'hot' methods (ones called frequently) directly into native mac

Java Interview Questions

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

Why is Java considered platform-independent, and what role does bytecode play in this?

What are the different memory areas allocated by the JVM (heap, stack, method area, PC register, native method stack), and what is stored in each?

Explain the Java classloader delegation model - how do the Bootstrap, Platform/Extension, and Application classloaders interact, and when would you need a custom classloader?

How does the JIT compiler improve performance over pure bytecode interpretation, and what is the difference between the C1 (client) and C2 (server) compilers?

Unlock the remaining 95 Java Questions & Verified Answers

Java Interview Questions

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

Why is Java considered platform-independent, and what role does bytecode play in this?

What are the different memory areas allocated by the JVM (heap, stack, method area, PC register, native method stack), and what is stored in each?

Explain the Java classloader delegation model - how do the Bootstrap, Platform/Extension, and Application classloaders interact, and when would you need a custom classloader?

How does the JIT compiler improve performance over pure bytecode interpretation, and what is the difference between the C1 (client) and C2 (server) compilers?

Unlock the remaining 95 Java Questions & Verified Answers