Comprehensive Java Learning Roadmap: Fundamentals, Core Java, JVM, Databases, Design Patterns, and Backend Development

1. Computer Fundamentals

1.1 Data Structure Basics

Key topics include vectors, linked lists, stacks, queues, heaps, dictionaries, trees, binary search trees, directed and undirected graphs, nine common sorting algorithms, various tree traversals (pre‑order, in‑order, post‑order, level‑order, zig‑zag), shortest‑path algorithms, and string algorithms such as KMP.

1.2 Operating Systems

Focuses on processes, threads, their differences, inter‑process communication, scheduling algorithms, memory management (virtual memory, paging, segmentation), file systems (linked and indexed), deadlock causes and prevention, and basic Linux commands plus scripting with shell and Python.

1.3 Computer Networks

Covers network layering models (five‑layer, seven‑layer, four‑layer), IP addressing, subnetting, supernetting, ARP, ICMP, gateways, VPNs, transport layer concepts (ports, UDP, TCP, three‑way handshake, four‑way termination), application‑layer protocols and ports, and deeper TCP/IP topics such as congestion control and sliding windows.

1.4 Fundamental Algorithms

Includes Big‑O notation, dynamic programming (e.g., knapsack variants, longest common subsequence), greedy algorithms (e.g., Huffman coding), B‑tree and B+‑tree for database indexing, and common graph algorithms like BFS, DFS, shortest‑path, and minimum spanning tree, with emphasis on having ready‑to‑use code for interviews.

2. Java Knowledge Basics

2.1 Java Basics

Recommended reading: "Thinking in Java". Master core Java technologies such as I/O, multithreading, reflection, and the collections framework; become familiar with Iterator, Iterable, Comparable, Comparator, and collection traversal and sorting; understand NIO, JMS, RPC, and core concepts like abstract classes versus interfaces.

2.2 Java Source Code

Study the source of HashMap, Hashtable, ConcurrentHashMap and their differences; explore other collection implementations like LinkedHashMap, LinkedHashSet, and Copy‑On‑Write; examine source code of Lock, Object, String, and related classes.

2.3 Java Concurrency API

Recommended books: "Java Multithreading Programming and Core Techniques" and "Java Concurrency in Practice". Topics include differences and usage of synchronized vs. Lock, wait/notify vs. await/signal, sleep vs. wait, other APIs like yield and join, volatile and CAS, lock implementations (spin lock, blocking lock, reentrant lock, biased lock), thread pools, blocking queues, and common concurrency patterns such as producer‑consumer.

2.4 Understanding the JVM

Recommended reading: "Deep Understanding of the Java Virtual Machine". Covers Java memory model and region allocation, reference types and reachability analysis, strong/soft/weak/phantom references, garbage collection mechanisms and algorithms, common OOM and SOF causes and solutions, JVM parameters, GC pauses, escape analysis, TLAB, off‑heap memory, major collectors (G1, CMS), performance monitoring tools (VisualVM, JConsole), class loading mechanism and parent‑delegation model.

3. General Knowledge Reserve

3.1 Databases

Recommended books: "MySQL Essentials" and "High‑Performance MySQL". Topics include common join queries, deep understanding of indexes, JDBC, database tuning techniques, differences between InnoDB and MyISAM, primary/foreign/unique indexes, views, triggers, cursors, stored procedures, and overview of relational (MySQL, Oracle) and NoSQL databases (Redis, HBase, MongoDB).

3.2 Design Patterns

Recommended book: "Design Patterns in a Nutshell". Emphasizes mastering various singleton implementations, recognizing design patterns in the JDK (e.g., decorator, adapter), common framework patterns (responsibility chain in Struts, factory in Spring, dynamic proxy), and the six SOLID principles.

3.3 HTTP Protocol

Recommended book: "HTTP: The Definitive Guide". Covers HTTP basics, protocol versions, using browsers to inspect requests/responses, request/response headers and bodies, and RESTful principles.

3.4 Spring Framework

Recommended books: "Spring in Action" and "Spring Internals". Topics include IoC principles, AOP concepts, XML configuration, transaction management, Spring MVC, webflow, remote services, REST, messaging, security, Spring Boot, and Spring Cloud.

4. Backend Learning Path

4.1 Web Backend Learning Path

Suggested resources on SSH integration. Topics: JSP and Servlet development, XML and JSON parsing, front‑end basics (HTML, CSS, JavaScript), JDBC, file upload/download, JavaMail, building simple projects with JSP/Servlet, then moving to frameworks such as Struts2, Hibernate, Spring, and their integration; later exploring Spring MVC, MyBatis, Lucene, Shiro, and building simple CMS projects.

4.2 Service Architecture Learning Path (optional for interviews)

Recommended book: "Distributed Service Framework Principles and Practice" and "Microservice Design". Covers SOA and microservices, load balancing (LVS, NGINX), RPC frameworks (RMI, Thrift), messaging (ActiveMQ), Netty communication, and service frameworks like Dubbo.

4.3 Hadoop Learning Path (optional for interviews)

Recommended book: "Hadoop: The Definitive Guide". Topics include MapReduce, HDFS, Hadoop cluster setup, ecosystem components (Zookeeper, Hive, HBase, Pig, Mahout), and Zookeeper usage as a registration center and configuration store.

Original source: cnblogs.com/nbalive2001/p/6418069.html