Io stream file read, write, and copy in Java

Construct File class

File F=new file (fileName);

Determine if the directory

F.isdirectory ();

Gets the file name under the directory

String[] Filename=f.list ();

Get the file under the directory
File[] Files=f.listfiles ();

1,Java How to read files

package com.yyb.file;  Import Java.io.File;  Import Java.io.FileInputStream;    Import Java.io.InputStream; /* * Read the file: * 1, locate the specified file * 2, create a file based on the file input stream * 3, create a byte array * 4, read the contents, put into the byte array * 5, close the input stream */public class FileRead {p Ublic static void Main (string[] args) {//build specified file filename = new ("E:" + file.separator + "Hello.tx          T ");          InputStream in = null;              try {//create file input stream according to file in = new FileInputStream (file);              Create byte array byte[] data = new byte[1024];              Read the contents and put it into the byte array in.read (data);          System.out.println (new String (data));          } catch (Exception e) {e.printstacktrace ();              } finally {try {//Close input stream in.close ();              } catch (Exception e) {e.printstacktrace (); }          }      }    }  

2, Java How to write files

Package com.yyb.file;    Import Java.io.File;  Import Java.io.FileOutputStream;  Import Java.io.OutputStream;    /  * * Write to File:  * 1, locate the specified file  * 2, the output stream according to file creation  * 3, convert content to byte array  * 4, write content to file  * 5, close input  stream  */ public class FileWriter {public        static void Main (string[] args) {          //build specified file filename          = new ("E:" + Fi Le.separator + "Hello.txt");          OutputStream out = null;          try {              //The output stream of the file created according to the file out              = new FileOutputStream (file);              String message = "I am a good man." ";              Convert content to byte array              byte[] data = Message.getbytes ();              Writes content              out.write (data) to a file,          } catch (Exception e) {              e.printstacktrace ();          } finally {              try {                  //Close output stream                  out.close ();              } catch (Exception e) {                  e.printstacktrace ()    }}}  

3. How to copy files in Java

<span style= "FONT-SIZE:18PX;"    >package Com.yyb.file;  Import Java.io.File;  Import Java.io.FileInputStream;  Import Java.io.FileOutputStream;  Import Java.io.InputStream;  Import Java.io.OutputStream; */* Implementation ideas: * 1, build source files and Target files * 2, the source file creates an input stream, the target file creates an output stream * 3, creates a byte array * 4, uses a loop, the source file reads part of the content, the target file writes part of the content, until all content is written * 5, close the source file input stream File output stream */public class FileCopy {public static void main (string[] args) {//build source file =          New File ("E:" + file.separator + "HelloWorld.txt");          Build target file FileCopy = new file ("D:" + file.separator + "HelloWorld");          InputStream in = null;          OutputStream out = null; try {//destination file does not exist to create if (! (              Filecopy.exists ())) {filecopy.createnewfile ());              }//source file Create input stream in = new FileInputStream (file);              The destination file creates an output stream out = new FileOutputStream (fileCopy, true); Create byte array byte[]temp = new byte[1024];              int length = 0; The source file reads part of the content while (length = in.read (temp))! =-1) {//target file writes part of the content OUT.W              Rite (temp, 0, length);          }} catch (Exception e) {e.printstacktrace ();                  } finally {try {///close file input/output stream in.close ();              Out.close ();              } catch (Exception e) {e.printstacktrace (); }}}}</span><span style= "FONT-SIZE:24PX;"   > </span>

　　

Io stream file read, write, and copy in Java