Someone finally sorted out the knowledge points that Java programmers must learn, which is very enlightening.

Someone finally sorted out the knowledge points that Java programmers must learn, which is very enlightening.

JVM

Regardless of the level of Java practitioners, JVM is a hurdle that must be overcome when advancing. Whether it is a job or an interview, JVM is a must-test question. If you don t understand the JVM, the salary will be very bad (nearly 70% of the interviewees hang on the JVM)

Introduced in detail about JVM thread, memory model, JVM runtime memory, garbage collection and algorithm, four reference types in Java, GC generational collection algorithm VS partition collection algorithm, GC garbage collector**, **JAVA IO/Major knowledge points of NIO and JVM class loading mechanism.

basic concepts:

JVM is a hypothetical computer that can run Java code, including a bytecode instruction set, a set of registers, a stack, a garbage collection, a heap, and a storage method domain. JVM runs on the operating system, it has no direct interaction with the hardware.

![](https://upload-images.jianshu.io/upload_images/20887676-0b0a9339017a39ee?imageMogr2/auto-orient/strip|imageView2/2/w/889/format/webp)

There are too many detailed knowledge points, and the copywriting is too long to see **"Java Core Knowledge System"**

![](https://upload-images.jianshu.io/upload_images/20887676-ebc4fbcb0d83f71b?imageMogr2/auto-orient/strip|imageView2/2/w/717/format/webp)

JVM directory

Java collection

Usually, our program needs to know how many objects to create according to the program running time. But if it is not for the program to run, at the stage of program development, we simply don't know how many objects are needed, or even the exact type of it. In order to meet these conventional programming needs, we require that any number of objects can be created at any time and anywhere, and what should be used to accommodate these objects? We first thought of arrays, but arrays can only hold uniform types of data, and their length is fixed, so what should we do? The collection came into being!

1. Interface inheritance and implementation

2. List

3. Set

4. Map

![](https://upload-images.jianshu.io/upload_images/20887676-7a8933943afc1afa?imageMogr2/auto-orient/strip|imageView2/2/w/880/format/webp)

Java collection framework diagram

There are too many detailed knowledge points, and the copy is too long, see **"Java Core Knowledge System"**, in which there is a detailed decomposition version of the collection diagram to correspond to each knowledge point (see table of contents)

![](https://upload-images.jianshu.io/upload_images/20887676-bcaacc8ec4cc1e82?imageMogr2/auto-orient/strip|imageView2/2/w/817/format/webp)

Java multi-threaded concurrency

Let's take a look at the concurrent knowledge base system diagram:

![](https://upload-images.jianshu.io/upload_images/20887676-c162ce7ac4e34c17?imageMogr2/auto-orient/strip|imageView2/2/w/1200/format/webp)

How to implement/create Java threads?

4 kinds of thread pools?

Thread life cycle (state)

4 ways to terminate threads

What is the difference between sleep and wait?

The difference between start and run?

Java background thread

Java lock

Basic thread method

Thread context switch

Synchronization and deadlock

Principle of Thread Pool

Java blocking queue principle

Usage of CyclicBarrier, CountDownLatch, Semaphore

The role of the volatile keyword (variable visibility, prohibit reordering)

How to share data between two threads?

ThreadLocal function (thread local storage)

The difference between synchronized and ReentrantLock

ConcurrentHashMap concurrency

Thread scheduling used in Java

Process scheduling algorithm

The concept and characteristics of threads

There are too many detailed knowledge points, and the copy is too long, see **"Java Core Knowledge System"**, in which there is a detailed decomposition version of the collection diagram to correspond to each knowledge point (see table of contents)

![](https://upload-images.jianshu.io/upload_images/20887676-81193b043f1ee240?imageMogr2/auto-orient/strip|imageView2/2/w/717/format/webp)

Deep analysis of spring principle

Spring is adopted by more and more microservice practitioners due to its many advantages. If you are proficient in Spring, you can become a leader in the field of rapid application development. However, you need to know why. This article will help you understand the operating mechanism behind Spring from the perspective of Spring source code and core implementation principles.

Introducing the catalog

Features of Spring

Spring's core components

Spring commonly used modules

Spring main package

Spring common annotations

Spring IOC principle

Spring APO principle

Spring MVC principle

Spring Boot principle

JPA principle

Mybatis cache

Tomcat architecture

![](https://upload-images.jianshu.io/upload_images/20887676-059c06117707dc06?imageMogr2/auto-orient/strip|imageView2/2/w/488/format/webp)

There are too many detailed knowledge points, and the copy is too long, see **"Java Core Knowledge System"**, in which there is a detailed decomposition version of the collection diagram to correspond to each knowledge point (see table of contents)

Forward this article and follow my private message reply [ architecture information ] Consult how to obtain **"Core Knowledge"**

![](https://upload-images.jianshu.io/upload_images/20887676-db04bc4c295a9cd3?imageMogr2/auto-orient/strip|imageView2/2/w/704/format/webp)

spring principle

Microservice

Microservice is a knowledge point that you have to master in the Internet industry today, and it is also the most popular and popular knowledge. Let's take a look!

Service registration discovery

API gateway

Configuration Center

Service tracking

Service fusing

API management

![](https://upload-images.jianshu.io/upload_images/20887676-824637a8de58d0c6?imageMogr2/auto-orient/strip|imageView2/2/w/777/format/webp)

There are too many detailed knowledge points, and the copy is too long, see **"Java Core Knowledge System"**, in which there is a detailed decomposition version of the collection diagram to correspond to each knowledge point (see table of contents)

Forward this article and follow my private message reply [ architecture information ] Consult how to obtain **"Core Knowledge"**

![](https://upload-images.jianshu.io/upload_images/20887676-8f1751a225cc5362?imageMogr2/auto-orient/strip|imageView2/2/w/549/format/webp)

Because the copy is too long, I won t introduce them here. The core knowledge summary knowledge points also include Netty and RPC, network, log, Zookeeper, Kafka, RabbitMQ, Hbase, MongoDB, Cassandra, 24 design patterns , Load balancing, database, consistency algorithm, Java algorithm, data structure, distributed cache and so on.

![](https://upload-images.jianshu.io/upload_images/20887676-ff9ed35d7619cd6d?imageMogr2/auto-orient/strip|imageView2/2/w/1200/format/webp)

This knowledge system is suitable for all Java programmers to learn. There are detailed explanations and introductions about the knowledge points in the above catalog. Mastering all the content of this knowledge point will give you a qualitative improvement. It also summarizes a lot of interview processes. A summary of the questions encountered and the corresponding answers.

Forward this article and follow my private message reply [ architecture information ] Consult how to obtain **"Core Knowledge"**

![](https://upload-images.jianshu.io/upload_images/20887676-ead21714996e5acf?imageMogr2/auto-orient/strip|imageView2/2/w/768/format/webp)
![](https://upload-images.jianshu.io/upload_images/20887676-44784e30c50c4119.jpg?imageMogr2/auto-orient/strip|imageView2/2/w/852/format/webp)