A test beginner listens to Java Video notes (i)

Build pho development environment and frame diagram Hanshunping

The first chapter:

No1 about the management of files and folders

The resulting text document is in the form of detailed information, showing file modification time and file size, facilitates file viewing and management, and is also a professional literacy requirement for an IT person to work efficiently. As shown in the following:

In order to facilitate the timely and correct Java files to find, the need for the computer environment configuration, to pay attention to four questions:

1, all folders in the hard disk Management, all settings. Click, Tools > View

2. Tick show files and all folders

3, remove the hidden known file extension to prevent the occurrence of classes such as XXX. Java.java

4, display the full path of the file, you can directly copy the application when needed, to avoid manual spelling errors.

5. Appears in Java. Bak file, is to indicate that Java files are automatically backed up when generated, such as to eliminate, you can go into the Java editor (note that Java itself) into the Advanced file configuration option to do unchecked file backup.

No2 Java compilation error No classs class case:

？

Javac detects if Java compilation was successful. Noclassdeffound ... Prompts for compilation errors. There is no definition for the class. (Def refers to a defined abbreviation)

Note the Java prompt for the error message. will tell the cause of the error.

Hint there is no definition of class possible cause:

1. No saving of class

The snowflake flag indicates that no disks have been saved, as shown in. Use CTRL + S to save.

2, environment variable configuration error. Environment variables can be re-set. Such as.

Configuring the Environment variable class path

No3: Understanding Java code Structure

• Code Structure anatomy:

1, class-class after Helloword for the class name, can be arbitrarily defined, the following left curly brace and the right curly brace (bottom) become the class body.

2, Main () refers to the method with curly braces to denote the method body.

3. There is only one public class in the source file, and you can define other classes, such as CLASST and common class.

4, Void indicates the return value

Teacher Summary ppt:

• The Java language Annotation classification and case.

Note: The comment does not affect the code run. The computer does not recognize the annotation language.

Three notes how to apply and learn to continue sharing.

No4: Knowledge of Java constants, variables,

Video location:

• Identifier

Focus on the last sentence, the identifier should be named to know, not with the Java language keyword, the Java language keyword in the code will be automatically marked with blue.

Attached:

• Constant:

Types of constants: summary

The constant value of the Java language is represented by a string.

String constants, often marked with double or single quotation marks

Question: What is the difference between a string constant and a character constant?

• Variables: variable definition and variable representation

In essence, a variable is actually a small chunk of memory, using the variable name to access the area, so each variable must be declared before it is assigned before it can be used.

Structure and type of variables

Local constants and member constants

Local variables: Variables in the method body

Member variable: Outside the method body variable, the variable within the member variable

All the variables in curly braces don't know the curly braces.

• Other

Arabic Letter one letter for a byte total of 8 bit

Chinese GBK

One character, 2 bytes, can be expressed in various languages.

Binary conversion to 16 binary converts the binary to decimal and then converts the decimal to 16 binary.

Learning process: Chapter Two concludes the first course.

A test beginner listens to Java Video notes (i)