Essential Java Interview Topics: From Core Concepts to Advanced Backend Skills

Java Interview Topics Overview

Overall interview process

Java cross‑platform principles

Setting up a Java development environment

Size of int in Java

Object‑oriented features of Java

Boxing and unboxing

Difference between == and equals

String handling

Java collections framework

ArrayList vs LinkedList

HashMap vs Hashtable

File copy utility: byte streams vs character streams

Thread creation, starting, and identification

Concurrency utilities and thread pools

Common design patterns

HTTP GET vs POST

Understanding Servlets and their lifecycle

Forward vs redirect in Servlets

JSP vs Servlet similarities and differences

Built‑in objects, scopes, and page data transfer

Session vs Cookie usage

MVC pattern and implementation

Database types and common databases

Three normal forms of relational databases

ACID properties of transactions

MySQL maximum connections

Pagination queries in MySQL and Oracle

Trigger use cases

Advantages of stored procedures

Calling stored procedures via JDBC

Understanding JDBC

JDBC example for Oracle

PreparedStatement vs Statement benefits

Purpose of database connection pools

HTML basics

Brief introduction to Ajax

Relationship between JavaScript and jQuery

Common jQuery selectors

jQuery document ready event

jQuery Ajax vs native Ajax

Overview of HTML5 and CSS3

What is Bootstrap

Definition of a framework

Introduction to MVC framework concepts

Struts2 execution flow and interceptors

Spring MVC workflow and differences from Struts2

Core concepts of Spring, AOP, and transaction propagation

ORM basics and differences between iBatis and Hibernate

Hibernate object states, caching, and usage

WebService scenarios

Brief intro to Activiti

Linux usage scenarios, common commands, and server operations

Cloud hosting considerations

Database optimization topics: schema design, indexing, partitioning, read/write splitting, caching, and SQL tuning

Redis usage, scenarios, data structures, eviction policies, and Java integration

WeChat public account development principles and project management basics