Javase Basic Note One

Self-study Java has been one months, it is time to tidy up the knowledge learned, review review, there are some places are not very understand, continue to refuel it.

Chapter One overview of the Java language

1. Software: System software vs application Software

2. People interacting with computers: using computer language.

Graphical interface vs. command line mode (dir MD rd CD CD: Cd/del exit)

3. Classification of languages: first generation: Machine Language second generation: assembly language Third generation: Advanced languages (Process & Object oriented)

4.java language Features: ① object-oriented ② robustness ③ cross-platform (write Once,run anywhere)---JVM java Virtual machine

5. Installing JDK and configuring environment variables

1) Install the JDK (Java Development Kit)

2) The Path:windows operating system executes the command-Request search path. (The path in the bin directory of the JDK is saved under the PATH environment variable)

3) Test: In the Command Line window, any file directory, the execution of Javac.exe or java.exe can be called successfully.

>JDK the relationship between the JRE JVM

6. How to write and run the first Java program

Procedure: Write----compile----run

1) Write: Each Java file is a. Java end, which becomes the source file. Java programs exist in the original file.

Class hellloworld{

The main method of the program is the entrance to the program

public static void Main (string[] args) {

The code to execute

System.out.println ("HelloWorld");

}

}

Note the point:

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

There can be at most one public class in a source file, with no limit to the number of other classes, and if the source file contains a public class, the file name must be named according to the class name.

The execution portal for Java applications is the main () method, which has a fixed writing format: public static void Main (string[] args) {...}

The Java 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: Executes the Javac.exe original file name in the directory where the source files are located. java; generates many bytecode files with a. Class ending.

3) Run: The generated bytecode file is executed through Java.exe interpretation.

7. Problems that occur in debugging programs

8. 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;

9.JDK documentation of all packages and classes provided by the--API

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Javase Basic Note One