J2SE (1) -- data basics, j2se -- data basics

J2SE (1) -- data basics, j2se -- data basics

The content in this article comes from the J2SE video of Jack Ma. The data foundation in Java is a computer language, which is similar to other programming languages. We know that if we call out the benefits, learning is easy.

(1) General diagram:

On the right side, the large to small inclusion relationship is: it will be clear at a glance.

(2) Details

The two pictures are one picture. If the previous picture is macro, the next picture is the details.

Identifiers, keywords, data types, expressions, element characters, statements, and methods are personally considered to be no different from other languages such as C.

New things learned here:

1. Pay attention to the location where the local variables and member variables are declared, and declare the referenced data type variables in the data type. I may not have much understanding about this in my previous studies, it is clear now.

2. What are the differences between character and string types? The difference is: the former uses single quotes, and the usage is used as a variable; the latter uses double quotes. The usage is used as a pointer and points to the first character.

3. recursion: As mentioned in the introduction to data structures, it is actually very simple. In a word, this method calls itself. For example:

public class Test{public static void main(String[] arg){System.out.println(method(<span style="font-family:KaiTi_GB2312;">4</span>));}public static int method(int n){if(n == 1)return 1;elsereturn n * method(n-1);}}

How can we understand this self-call?

It's clear!

(3) summary:

Remember: The format is more important than the algorithm!

What is j2se?

J2SE: java 2 Standard edition (java 2 Standard edition), java2 Platform
In general, we can understand that J2SE is the foundation.
 
Q: What is j2se? How to Learn j2se?

As far as my personal experience is concerned, learning J2SE is mainly to learn the Java language itself and its programming ideas. As for the technology or skills in J2SE, it is rarely used in J2EE. therefore, to learn J2SE, we should focus on the language and programming ideology, lay a good foundation for Object-Oriented Programming, and learn the design mode if you have the energy, these things in J2SE are the essence of the Java language. on that platform, both EE and ME can be used, and if you can well apply object-oriented design ideas and appropriate design patterns, you will be comfortable and fun when developing large systems, otherwise, development under J2EE will suffer you. and when you have a good object-oriented foundation, you will be easily promoted to a project manager in the future. To be honest, Chinese programmers have a rare understanding of object-oriented design principles and design patterns.

I have nothing to say about the learning sequence of J2EE. In fact, there is no order at all, just step by step. don't be impetuous. don't go to learn about Servlet because it's out of date. if you want to apply it, you can select a development framework that is not currently the mainstream for further study. if you want to enter a foreign company in the future, do not study those open-source products. large foreign companies will not use those open-source products. You can study IBM's
Websphere or Oracle.

As for employment, a good enterprise pays little attention to what it will do, but cares about what you have done. Therefore, you should not only ignore the practice in the course of study, but have the opportunity to practice more, seize all the opportunities for internships at school and try to do a few small projects as much as possible. This requires you to go out and find a job after graduation.

After talking about this, we can sum up learning J2SE focuses on the understanding of programming ideas. During the learning process, we should not be impetuous, rather than learning technologies that we think are outdated. Instead, we should not just be eye-catching, finding a job by accumulating experience in the future.

The AWT and Swing in J2SE do not need to be looked at, and the general network framework does not need to be looked at carefully.
2. You do not need to recite the code. The key is to understand the spirit. The learning mode cannot be finalized. You must be able to bypass the concept on the basis of understanding your thoughts.
3. Being proficient in using a good development framework can not only greatly improve development efficiency, but also make your program more efficient and robust. Therefore, learning to use a good framework is necessary.
4. The database part is of course very important, but for J2EE developers, they must be familiar with the basic functions of the database, use SQL statements to add, delete, modify, and query, and master the database connection and access principles. if the architecture can be implemented in the future, you also need to master the database design, deployment, and optimization.