Java IO file read and write example (Outputstream,inputstream,writer,reader)

One, file creates files

File File = new file ("D:" + file.separator + "Yi.txt");

code example:

 PackageCom.hbut.io;ImportJava.io.File;Importjava.io.IOException; Public classFiledemo { Public Static voidMain (string[] args) {File file=NewFile ("D:" + file.separator + "Yi.txt"); if(File.exists ()) {file.delete (); System.out.println ("File already exists"); } Else {               Try {                  Booleanstates=false; States=File.createnewfile (); if(states==true) {System.out.println ("File creation succeeded"); }            } Catch(IOException e) {//TODO auto-generated Catch blockE.printstacktrace (); }           }       }   }  

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Two, OutputStream (byte stream) write file

out= new FileOutputStream (file);//Get the actual byte stream output object, content overlay

String info= "Hello";//What to enter

Byte[] B=info.getbytes ();//convert character to byte array

Out.write (b);

code example

 PackageCom.hbut.io;ImportJava.io.File;Importjava.io.FileNotFoundException;ImportJava.io.FileOutputStream;Importjava.io.IOException;ImportJava.io.OutputStream; Public classOutputdemo { Public Static voidMain (string[] args) {File file=NewFile ("D:" + file.separator + "Yi.txt");//specify the file to write toOutputStream out=NULL;//define a byte stream output object        Try{ out=NewFileOutputStream (file);//gets the actual byte stream output object, covering the contents of the}Catch(FileNotFoundException e) {e.printstacktrace (); } String Info= "Hello";//What to enter        byte[] b=info.getbytes ();//Convert a character to a byte array        Try{out.write (b); } Catch(IOException e) {e.printstacktrace (); }           Try{out.close (); } Catch(IOException e) {e.printstacktrace (); }       }   }  

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Third, InputStream (byte stream) read out the file

InputStream in = null;//defines a byte stream input object

in = new FileInputStream (file);//Get the actual byte stream input object

Byte[] B = new byte[1024];//open space, read content

Len = In.read (b);//Read

System.out.println (New String (b, 0, Len));//Output Read content

code example

 PackageCom.hbut.io;ImportJava.io.File;ImportJava.io.FileInputStream;Importjava.io.FileNotFoundException;Importjava.io.IOException;ImportJava.io.InputStream; Public classInputstreamdemo { Public Static voidMain (string[] args) {File file=NewFile ("D:" + file.separator + "Yi.txt");//Specify the files to readInputStream in =NULL;//defining a byte stream input object        Try {            //out= New FileOutputStream (file,true);//whether the byte append functionin =NewFileInputStream (file);//get the actual byte stream input object}Catch(FileNotFoundException e) {e.printstacktrace (); }        intlen = 0;//Input Array Length        byte[] B =New byte[1024];//open space, read content//byte[] b=new byte[(int) file.length ()];//open up space based on file size        Try{len= In.read (b);//Read}Catch(IOException E1) {e1.printstacktrace (); }        Try{in.close (); } Catch(IOException e) {e.printstacktrace (); } System.out.println (NewString (b, 0, Len)); }}

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Four, writer (character stream) write file

Writer Write = null;//defines the character output stream

Write = new FileWriter (file);

String infor = "Hello,writerdemo";//information that will be written to the file

Write.write (infor);//write file

code example

 PackageCom.hbut.io;ImportJava.io.File;ImportJava.io.FileWriter;Importjava.io.IOException;ImportJava.io.Writer; Public classWriterdemo { Public Static voidMain (string[] args) {File file=NewFile ("D:" + file.separator + "WriterDemo.txt");//specify the file to write toWriter Write =NULL;//defining the character output stream        Try{Write=NewFileWriter (file); } Catch(IOException e) {e.printstacktrace (); } String infor= "Hello,writerdemo"; Try{write.write (infor); } Catch(IOException e) {e.printstacktrace (); }        Try{write.close (); } Catch(IOException e) {e.printstacktrace (); }    }}

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Five, reader (character stream) read out the contents of the file

Reader Read = null;//defines the character input stream

Read = new FileReader (file);

Char[] B=new char[1024];//Set the length of the character

int Len=read.read (b);//file contents read into b[]

System.out.println (New String (b));

code example

 PackageCom.hbut.io;ImportJava.io.File;ImportJava.io.FileReader;Importjava.io.IOException;ImportJava.io.Reader; Public classReaderdemo { Public Static voidMain (string[] args) {File file=NewFile ("D:" + file.separator + "Yi.txt");//specify the files to be read outReader Read =NULL;//defining character input streams        Try{Read=Newfilereader (file); } Catch(IOException e) {e.printstacktrace (); }           Char[] b=New Char[1024];//set the length of a character        Try {               intlen=Read.read (b); System.out.println (NewString (b)); } Catch(IOException e) {e.printstacktrace (); }           Try{read.close (); } Catch(IOException e) {e.printstacktrace (); }       }   }  

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Java IO file read and write example (Outputstream,inputstream,writer,reader)