Other JAVA Learning (I) basic knowledge and java learning basic knowledge

Other JAVA Learning (I) basic knowledge and java learning basic knowledge

In the past, machine learning in Python found that when the data volume is getting bigger and bigger, it is hard to meet the needs of simple python processing,

Hadoop needs to be used for parallel data processing, while hadoop is written in JAVA, so I started learning JAVA.

The following are study notes:

There are a total of nine chapters. The general idea of the chapter is: Why ---> what ---> how to do it.

About why?

The objective is simply to achieve more effective concurrent data processing.

What?

Welcome to the world of JAVA.

I. Basic Knowledge

1. Software Development

A: What is software?

Software: a collection of computer data and commands organized in a specific order.

Common Software: system software, such as DOS, windows, and Linux,

Application Software: such as mine clearance, thunder, and QQ.

B: What is development?

Production Software

2. Human-Computer Interaction

A: The emergence of software enables better interaction between people and computers.

B: Interaction Mode:

Graphical User Interface GUI)

This method is simple, intuitive, and easy to use.

Command Line Interface CLI)

A console is required to enter specific commands for the computer to complete some operations.

This is troublesome. You need to record some commands.

3. Command Line

Doscommand line, a common command in the course.

Dir: list files and folders in the current directory

Md: create a directory

Rd: delete a directory

Cd: Enter the specified directory

Cd ..: Return to the upper-level directory

Cd \: Return to the root directory

Del: delete an object

Exit: releases the doscommand line.

4. Computer Language

A: through the demonstration of the doscommand line, we found that the operation on the computer is the same as that on the computer.

B: Let's tell it what it can do. The premise is that we and what it says must be identified. This is the computer language.

4.1. What is a computer language?

A: Language: communication between people.

For example, Chinese people communicate with Chinese people in Chinese.

Chinese people need to learn Korean if they want to communicate with South Koreans.

B: computer language: communication between people and computers.

If people want to communicate with computers, they need to learn computer languages.

There are many computer languages, such as C, C ++, and JAVA.

4.2 Java language Overview

A: It is a high-level programming language launched by SUN (Stanford University Network, Stanford University Network company) in 1995.

B: It is an Internet-oriented programming language.

C: as Java technology continues to mature in the web field, it has become the preferred development language for Web applications.

D: it is a language that is easy to learn, fully object-oriented, secure and reliable, and has nothing to do with the platform.

E: three technical architectures

J2EE (Java 2 Platform Enterprise Edition) Enterprise Edition

J2SE (Java 2 Platform Standard Edition) Standard Edition

Small Edition of Java 2 Platform Micro Edition

F: language features: cross-platform

What is the principle?

To run a java application,

First install a Java Virtual Machine (JVM Java Virtual Machine.

JVM is responsible for running Java programs in this system.

4.3 Java environment setup

A: clarify what is the JRE (Java Runtime Enviroment) Java Runtime Environment, JDK (Java Development Kit) Java Development Kit

B: Download JDK

C: Install JDK

D: Configure Environment Variables

E: Check whether the verification is successful

4.4 Java program development experience-Hello World

Write Java code to a file with the extension. java.

Use the javac command to compile the. java file.

Run the generated class file using java commands.

In short: Write --> compile --> RUN

4.5 configure classpath

Classpath query order: first find the path defined in path, and then find it at the moment;

Path search order: Find the path first, and then find the path.

Highlights of this chapter:

Features of JDK, JRE, and JVM

Environment variable configuration path and classpath and their functions.

Java programming, compilation, and running steps.

Common Errors and solutions in configuration, writing, compilation, and running steps.

The next chapter describes the basic components of the Java language.

We recommend that you use a java book to systematically learn java, from basic learning (with the basis of java), but want to systematically learn java

Good question,
1. It has a solid foundation and is very helpful.
2. Be proficient. It takes a long time to invest.
Write down my personal feelings. There are a lot of answers to these questions on the Internet,
1. Start with the java syntax. Many people think that these things are very simple. They may be finished in one day or one morning. However, the most important details of all things are god in details. After you finish reading them, let's take a look at the questions of scjp and check your own skills. You do not need to take this certification, but actually realize your understanding of java. At this stage, you can take a look at some java training courses. It seems that there is a person named Zhang xiaoxuan, which is suitable for people without other language basics. If you have a basic knowledge, you can take a look at thinking in java.
2. Then, in some stages of improvement, after you are familiar with the java syntax, you are familiar with the java language. The best way to be familiar with the language is to familiarize yourself with its class library, I personally recommend that the best book is core java. Now it is 7 or 8. I think it is 6. This book is the most popular java book I know.
3. When you are familiar with both the syntax and language to a certain extent, you need to know it and then understand it. (The premise is that you want to be truly proficient in this language, otherwise, jsp can be implemented at this time. At this time, the site should have a higher angle. First, let's look at jvm. Now, according to my opinion on this method in China, there is no particularly good book, since there are not a few articles, after learning how java runs. Imagine how to implement a java program and use the source code of jdk with this problem. There is a book called effect java, which should have been about the most basic things, but it is very difficult. At this stage, the results will be very different.

4. After the first three phases of real time and a solid java Foundation, we can start to look at the most popular java fields, starting with servlet and jsp, and then those J2EE things. Those things have more design concepts and design patterns in essence. There is a book called java and pattern, which seems to be written by ghost. It is an entry-level book with a good design pattern. When I was reading a book, I had to broaden my mind. If I wanted to implement tomcat myself, where should I start? If I had such an idea, I would like to understand tomcat, it must be more profound than most people.
5. After learning the above things to a certain extent, we should pay more attention to methodology things at that time. Including the software development model and the methodology of program design. This stage is relatively high. I did not study it deeply. I could not provide too many things. I could only provide some terms, such as refactoring and agile development. In foreign countries, it seems like a martin, Robert, and so on.

All of the above processes require a lot of hands-on practices, no practices, learning all programming languages is just a waste of water, a mirror of the month, but also to practice. If you have a good attitude (this is the most important thing), don't be tempted to deviate from this direction when others start to learn J2ee and other things, xuanmen's hard work is very difficult to get started, and then it is faster and faster. The opposite is true for the nine-yin and white-bone claw. In the process of learning, nothing else matters. The most important thing is diligence and rewards.

You can learn Java in 16 hours a day.

If you spend 16 hours learning every day, I believe you will have good grades.
I suggest that you do not learn your knowledge, but your health should be exhausted.