File operation serialization recursive copy

1、  File

1、1 summary  

java.io.File class ： Abstract representation of file and file directory paths , It's not about the platform

File It can be built 、 Delete 、 Rename files and directories , but File Can't access the file content itself .

If you need to access the file content itself , You need to use input / Output stream .

Want to be in Java A program that represents a real-life file or directory , Then there must be a File Yes like , however Java One of the procedures File object , There may not be a real file or directory .

File Object can be passed as a parameter to the constructor of the stream

1.2  Construction method

public File(String pathname) With pathname Create... For the path File object , It can be absolute path or relative path , If pathname Is a relative path , The default current path is in the system property user.dir Storage in .

Absolute path ： It's a fixed path , Start with the drive

Relative paths ： It's about starting from a certain position

public File(String parent,String child) With parent The path of fatherhood ,child Create... For the subpath File object .

public File(File parent,String child) According to a father File Object and sub file path creation File object

1.3  Common methods

Acquisition function ：

public String getAbsolutePath()： Get absolute path

public String getPath() ： Get path

public String getName() ： Get the name

public String getParent()： Get the upper file directory path . If there is no , return null

public long length() ： Get file length （ namely ： Number of bytes ）. Cannot get the length of the directory .

public long lastModified() ： Get the last modification time , Millisecond value

public String[] list() ： Get the name array of all files or file directories in the specified directory

public File[] listFiles() ： Get all the files in the specified directory or file directory File Array

Rename function ：

public boolean renameTo(File dest): Rename the file to the specified file path

Judgment function ：

       public boolean isDirectory()： Determine whether it is a file directory

public boolean isFile() ： Determine if it's a document

public boolean exists() ： Judge whether it exists

public boolean canRead() ： Judge whether it is readable

public boolean canWrite() ： Judge whether it is writable

public boolean isHidden() ： Determine whether to hide

Create delete function ：

       public boolean createNewFile() ： create a file . If the file exists , Do not create , return false

public boolean mkdir() ： Create file directory . If this file directory exists , We won't create . If the upper directory of this file directory does not exist , It doesn't create .

public boolean mkdirs() ： Create file directory . If the upper file directory does not exist , Create... Together

matters needing attention ： If you create a file or the file directory does not have a drive letter path , that , Default in project Under the path .

public boolean delete()： Delete files or folders

Delete notes ：

Java Delete in does not go to the recycle bin .

To delete a file directory , Please note that the file directory cannot contain files or file directories

1.4  Usage mode

 

 1.5  Recursive replication  

1 Copy

Is the combination of input and output

2 Get all sub files under the folder

If the sub file is a file , Copy

If the sub file is a directory, then obtain all the sub files of the directory , Do the same thing

Be careful :

When copying , The source directory and destination directory cannot be consistent

 

 2、 Object flow  

2.1  summary

 2.2 Be careful

  The class to serialize must implement Serializable Interface , This interface is an identifier

This class can be serialized

2、3 serialize

 2.4 Deserialization

 2.5  serial VersionUID

 2.6 Transient