d: Enter letter to switch
dir: list the current directory files and folders
md: Create a directory
rd: delete the directory (delete the folder)
cd: change the specified directory, into the specified directory
cd ...: return to the parent directory
cd: return to the root directory
del: delete files, delete files, like a bunch of extension * .txt (only deleted files can not be deleted folders)
CLS (the clear screen): clear screen
exit: exit.
JRE: JAVA runtime environment (required JAVA virtual machine and the JAVA program library), JVM + class library (core libraries)
the JDK: JAVA development environment (including Java development tools), the JRE + Tools
the JVM: to ensure cross-platform program
Frequently Asked Questions:
1 extension is hidden.
The same name with the file extension 2.
3 JAVA strictly case-sensitive.
4 see illegal characters: \ 65307 is certainly Chinese problem, we want to write the punctuation all in English state.
5 brackets in pairs.
Uninstall the software:
green version: delete files directly
install version: via the control panel to uninstall or professional management software uninstall
Configuration path environment variable effect: the end of any exe files in any directory can go with. The record is an executable file, such as: exe file. Java is the role of the javac command can be run in any directory.
Configuring classpath environment variable role: the role of imitation path, arbitrary class files can be used in any directory. classpath record is to run Java class files.
Note:
two %% equivalent to reference configuration system variables.
The key word consisting of all lowercase.
Identifiers have uppercase and lowercase letters, numbers, underscores, $ specifier can not start with a number.
Java language strictly case-sensitive.
Naming rules: See name known meaning.
Document Note: javadoc is parsed to generate a description, to explain the object-oriented portion. / ** /
// single line comment / * / multi-line comment
integer default is int type
floating type double default
long integer or a suffix l L mark recommended L.
Single precision floating point or a suffix f flag F, F recommended
cast from weak to strong type conversion type: byte, short, char-> long- > float-> double
cast formats: the target data type variable = (target data type) (converted data)
constant, the calculated first result, and see if the byte in the range of, if not in error.
Sign bit: 1 is negative, 0 is a positive number.
Common ASCII values:
'A' 97
'A' 65
'0' 48
character string data and other data do +, the result is a string type.
+ + Not here, but a string concatenation operator.
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