Java language in-depth files and streams

There are too many classes in the java I/O system. Here we only learn some basic and commonly used ones. I believe that if we can master these, we can solve our common applications in the future

1. What is data flow?
Data flow Refers to all data communication channels. There are two types of streams, InputStream and OutputStream. The basic functions of each stream in Java depend on them. InputStream is used for read, and OutputStream is used for write. Reading and writing are relative to memory. , reading is to bring data into the memory from other places, and writing is to push the data out of the memory. These two are abstract classes and cannot be used directly.
2. The methods of InputStream are:
read() reads data from the stream. There are 3 ways:
int read() reads one byte at a time
int read(byte[]) reads multiple bytes into an array
int read(byte[],int off,int len) specifies where in the array to start from Start, read how long
skip() skips several bytes in the stream
available() returns the number of available bytes in the stream, but is invalid when based on the network, returns 0
markSupported() determines whether mark and reset operations are supported
mark( ) Mark a position in the stream, to be used in conjunction with markSupported()
reset() Returns the marked position
close() Closes the stream
3. OutputStream method:
write(int) Writes a byte to the stream
write (byte[]) Write the contents of the array to the stream
write(byte[],int off,int len) Write the len length of data in the array starting from the position specified by off to the stream
close() Close the stream
flush() forces the data in the buffer to be output
4.File class
File can represent files or directories. The File class controls all hard disk operations
Constructor:
File(File parent,String child) Use parent class and File name construction
File(String pathname) is constructed with absolute path
File(String parent,String child) is constructed with parent directory and file name
File(URI uri) is constructed with remote file
Common method:
boolean createNewFile();
boolean exists();

Example:
//Create test.txt file object, determine whether it exists, create it if it does not exist
import java.io.*;

public class CreateNewFile{
public static void main(String args[ ]){
File f=new File("test.txt");
try{
if(!f.exists())
f.createNewFile();
else
System.out.PRintln("exists") ;
}catch(Exception e){
e.printStackTrace();
}
}
}

boolean mkdir()/mkdirs()
boolean renameTo(File destination)
Example: //Look at this mkdir() The difference between /mkdirs() and the usage of renameTo
import java.io.*;
public class CreateDir{
public static void main(String args[]){
File f=new File("test.txt");
File f1=new File("Dir");
File f2=new File("Top/Bottom");
File f3=new File("newTest.txt");
try{
f.renameTo(f3);
f1.mkdir();
f2.mkdirs();
}catch(Exception e){
e.printStackTrace();
}
}
}

String getPath()/getAbsolutePath()
String getParent() /getName()
Example: //There is no parent directory and test.txt file on the hard disk, but we can still operate because we created their objects and operate on the objects
import java.io.*;
public class Test{
public static void main(String args[]){
File f=new File("parent/test.txt");
File f1=new File("newTest.txt");
try{
System .out.println(f.getParent());
System.out.println(f.getName());
System.out.println(f1.getPath());
System.out.println(f1.getAbsolutePath ());
}catch(Exception e){
e.printStackTrace();
}
}
}

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