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 .
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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)