Read 30 minutes before going to bed every day_ day4_ Files

Access items in the directory

1. Get all directories and files in the current path （ Get subdirectories non recursively ）list Method

•  Stream<Path> pathLists = Files.list(path);
  

2. Get all directories and files in the current path （ Get subdirectories recursively ）walk Method

• Stream<Path> walkPaths = Files.walk(path);
  

3. Get all directories and files in the current path （ Get subdirectories recursively （ The specified depth is 2））walk Method

• Stream<Path> walkPathsDepth = Files.walk(path, 2);
  

4. Get the properties of the file readAttributes（） Method

**{@code “*”} then all attributes are read.** adopt Pass in the parameter * You can get all attributes

• Map<String, Object> attrMap = Files.readAttributes(path, "*", LinkOption.NOFOLLOW_LINKS);
  

• Set<String> keySet = attrMap.keySet();
  

• keySet.forEach(key -> System.out.println(key));
  

• System.out.println(attrMap.get("lastAccessTime"));
  

The result is map The saved

5.FileChannel Call static methods open Create channels , Parameters （path,StandardOpenOption）

• Path pa = Paths.get("O:\\code\\BeforeSleeping30m\\testData\\my\\my1.txt");
  FileChannel channel = FileChannel.open(pa, StandardOpenOption.APPEND);
  

StandardOpenOption Yes WRITE,APPEND,TRUNCATE_EXUSTING（ If a file exists when writing , Delete the original ）,CREATE

6.Buffer class （ByteBuffer,CharBuffer） etc.

• get： obtain buffer Bytes in

• put： towards buffer Push bytes in

• clear() : The pointer is reset to 0, The limit is set to capacity , Prepare for writing

• flip： Read write conversion , After reading , You need to get the content , Before getting the method, you need to call , Return the pointer to 0;

• rewind： The read / write position pointer returns 0, Prepare for rewriting .

• remaining： Returns the number of remaining values read in or written out ;

        Path pa = Paths.get("O:\\code\\BeforeSleeping30m\\testData\\my\\my1.txt");
        FileChannel channel = FileChannel.open(pa, StandardOpenOption.APPEND);
        String s = "I am a man";
        ByteBuffer buffer = ByteBuffer.wrap(s.getBytes());
        int i = channel.write(buffer);
        // Read write conversion 
        buffer.flip();
        // Set the pointer position to 0
        buffer.rewind();
        long position = channel.position();
        System.out.println(" channel.size() "+ channel.size());
        System.out.println("position:"+ position);
        // Position reset to 0, The limit is set to capacity 
        buffer.clear();
        channel.close();
        System.out.println();

All the codes of this test ：

import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.*;
import java.util.Map;
import java.util.Set;
import java.util.stream.Stream;

/** * @Author Janson * @Date 2022/4/20 9:17 * @Version 1.0 */
public class Day4_Files {
    
    public static void main(String[] args) throws Exception  {
    
        Path path = Paths.get("O:\\code\\BeforeSleeping30m\\testData");

        //list Method does not enter subdirectories . As can be seen from the results 
        Stream<Path> pathLists = Files.list(path);
        pathLists.forEach(pathList->System.out.println("testData All directories under （ The subdirectory path of the directory will not be read ）：" + pathList));

        //walk Method Society   Read all directory paths under the directory , Include subdirectories 
        System.out.println("================ Split line ==================");
        Stream<Path> walkPaths = Files.walk(path);
        walkPaths.forEach(walkPath->System.out.println("test All directories under （ The path of subdirectories in the directory will also be read ：）"+ walkPath));

        System.out.println("================ Split line ==================");
        // Specify the depth of traversing subdirectories 
        Stream<Path> walkPathsDepth = Files.walk(path, 2);
        walkPathsDepth.forEach(walkPathDepth -> System.out.println(" The specified depth is 2 layer ：" + walkPathDepth));

        // Get the properties of the file 
        //{@code "*"} then all attributes are read.
        // LinkOption.NOFOLLOW_LINKS  Don't follow the symbolic connection 
        Map<String, Object> attrMap = Files.readAttributes(path, "*", LinkOption.NOFOLLOW_LINKS);
        Set<String> keySet = attrMap.keySet();
        keySet.forEach(key -> System.out.println(key));
        System.out.println(attrMap.get("lastAccessTime"));

        Path pa = Paths.get("O:\\code\\BeforeSleeping30m\\testData\\my\\my1.txt");
        FileChannel channel = FileChannel.open(pa, StandardOpenOption.APPEND);
        String s = "I am a man";
        ByteBuffer buffer = ByteBuffer.wrap(s.getBytes());
        int i = channel.write(buffer);
        // Read write conversion 
        buffer.flip();
        // Set the pointer position to 0
        buffer.rewind();
        long position = channel.position();
        System.out.println(" channel.size() "+ channel.size());
        System.out.println("position:"+ position);
        // Position reset to 0, The limit is set to capacity 
        buffer.clear();
        channel.close();
        System.out.println();

    }
}