Learning is like building a house. It is very important to lay a good foundation. How high a house can be built depends on the foundation. Learning the same truth, basic knowledge is the necessary condition to learn all technology later, we are preparing to learn a development language, first of all to learn its foundation, not only to be able to, but also to master; No matter how the technical framework changes, the essence is to encapsulate the basic reinvention. Object-oriented programming (OOP) : The most important idea of OOP is class. A class is a template. An object is constructed from a class, that is, an instance of the class is created. 2. Encapsulation: It is the realization process of combining data and behavior and hiding data from object users. Usually, the data in an object is called his instance field. 3. Inheritance :Java allows you to build new classes from existing classes. When you inherit an existing class, you reuse the methods and fields of that class, and you can add new methods and fields to the new class. Polymorphic: In Java, object variables are polymorphic; Note that multiple inheritance is not supported in Java; 5. Relationships between classes: use-a: dependency; Has-a: aggregation relation; Example: Class A inherits class B. At this time, class A not only has the methods of class B, but also has its own methods. Constructor is a special method that constructs objects and initializes them. Constructor features: Constructors can have zero, one or more parameters.
The constructor and class names are the same;
A class can have multiple constructors;
The constructor returns no value;
The constructor must be used with the new operator;
Network diagram 7. Package Java allows one or more classes to be grouped together into a group, called a package, for better management. Standard Java libraries are divided into many packages such as java.lang, java.util, Java, NET, etc. Packages are hierarchical, and all Java packages are in the Java and Javax package hierarchy. 8. Overloading: Overloading occurs when multiple methods have the same name but different parameters. The compiler selects which method to call. 9, robust features :Java adopts a safe pointer model, can effectively prevent overwriting memory and data crashes; 10, security :Java can be used to build anti-virus and anti-attack system, the fact that Java in anti-virus aspects do better; 11, portability :Java has strict rules on the size and algorithm of basic data structure types, so it has good portability; 12, multithreading: because of the mechanism of Java, it is very simple to deal with multithreading process,Java to achieve multithreading to the following operating system or thread procedures to complete, so multithreading is Java as a server-side development language popular one of the reasons; Dynamic binding: This is Java’s mechanism for calling object methods. 14. Every class in Java extends from the Object class. Inner class: An inner class is defined in another inner class. This is just a list of the most important things you need to know. Novice according to this learning route: the first stage: HTML+CSS static layout start, some people can say that I am doing back-end, front-end things do not have to take care of, this itself is a misunderstanding, now HTML5 is so powerful, you will not have any competitiveness. The second stage: JS/JQ JS must be mastered is particularly important, but also the most difficult, needless to say, JavaScript whether in the front-end or back-end is a very large proportion, a lot of people do not understand is reasonable, this is related to thinking, appropriate understanding of the data structure is conducive to learning JavaScript and Javase. The third stage: the foundation of JAVA, the core technology of JAVASE, the soul of JAVA and the database closely connected with JAVA. The most important JAVASE, I think we all know that JAVASE is the basic part of JAVA, people who have studied know that 80% of any paper is the basis, nothing too difficult, JAVASE is the foundation of JAVA, according to my so many years of learning JAVA experience, if a person can not learn JAVASE, JAVA is basically a blank SLATE, and the framework behind it is basically a blank SLATE. Database, no need to say, the most common of the three databases, add, delete, change, more to practice SQL statements, complex connection said difficult. JSP and Servlets As of today, some companies do not use JSP because it is a bit slow to load. But learn it now, because it is also important in JAVA architecture: JAVAEE enterprise development, framework, Struts2, Hibernate4, Mybatis3, Spring4, Spring MVC, these things need to be mastered, but the whole JAVA representation to understand is still a bit difficult indeed, self-study, The first problem many beginners encounter when learning Java is configuring environment variables on their computer after installing the JDK. Configuration of environment variables is indeed a bit difficult, if you encounter problems here, you can private message me Q3300863615, self-learning Java must be online to find some Java tutorials. I found a lot of videos and found that there is a big difference between good and bad Java video tutorials. Some tutorials are just part of the story, while others have a higher threshold of content and are not suitable for beginners. Xiaobian suggest a look. Download the API documentation and look at it often. While the API documentation may seem a bit geeky to many Java novices, it’s a good idea to get started if you take your time. Also, any Java program can’t live without API documentation, so embrace it. Self-study Java, must not be lazy, not only to learn, but also to practice, only their own practice, in order to have a sense of code, in order to truly understand packages, classes, methods, variables and some keywords of the inherent meaning. So, learn to code as you go along. Teach yourself Java, and even better, figure out why you want to learn Java. Learning a programming language is difficult for non-professionals, so we should be clear about why we want to learn Java and determine our goals earlier, so that we don’t wander aimlessly and have the motivation to move forward. The above learning content basically includes all, JAVA system basic above, hope to learn JAVA beginners can stick to it, JAVA language is really very powerful, in order to need talent is also the most