Java language Overview (0)

Java Language Overview

1. Software: System software vs application software

2. Classification of languages: first generation: Machine language

second generation: assembly language

third generation: high-level languages (process-oriented --- object oriented)

features of the 3.java language: ① face ② robustness ③ cross-platform (write Once,run anywhere)---JVM

4. installing The JDK and configuring the path environment variable

1) Install the JDK in a fool's style

2) Configure the path environment variable

> riverbed is like the bottom of the operation,JDK Like the river,Java The application is like a ship

Note: JDK JRE JVM

5. How to write and run the first Java program

"Process" writing---> Compiling---> Running

① Writing : Each Java file is a. Java end, called the source file "Helloworld.java". The Java program exists in the source file.

Class helloworld{//The Main method of the program, is the entry of the program public static void Main (string[] args) {//Executed code System.out.print    ln ("HelloWorld"); }}

Note the point:

• the Java source file has a "java" extension. The basic component of a source file is the class, such as the HelloWorld class in this class .
  

• A source file can have up to one class. The number of other classes is unlimited if the source file contains a class, the file name must be named by the class name.

• Java the application's execution portal is Main () method. It has a fixed writing format:publicstatic void Main (string[] args) {...} L Java The language is strictly case sensitive.

• the Java method consists of a few statements, each with a ";" End.
  

• Curly braces are all in pairs, indispensable.

② Compile: in the directory where the source files are located, execute the javac.exe source file name. java; generate many bytecode files with a. Class ending

③ run: generated bytecode file interpreted by Java.exe

6. Problems that occur in debugging programs

7. Note: ① single-line comment//② Multiline comment/* * * (Multi-line comment cannot be nested) ③ document Comment/** */javadoc-d file directory name-author-version source file name. java;

8.JDK documentation for all of its packages and classes: API

Java language Overview (0)