Java read-write file encyclopedia

Original: http://www.open-open.com/code/view/1423281836529

Java in a variety of ways to read the file one or more ways to read the contents of the file. 1, read file contents by byte2, read file contents by character3, read file contents by line4, Random Read file contents*/ImportJava.io.BufferedReader; ImportJava.io.File; ImportJava.io.FileInputStream; ImportJava.io.FileReader; Importjava.io.IOException; ImportJava.io.InputStream; ImportJava.io.InputStreamReader; ImportJava.io.RandomAccessFile; ImportJava.io.Reader;  Public classReadFromFile {/*** Read files in bytes, often used to read binary files, slices, sounds, images, and other files. * @paramthe name of the filename file*/    Public Static voidreadfilebybytes (String fileName) {File file=NewFile (fileName); InputStream in=NULL; Try{System.out.println ("reads the contents of the file in bytes, one byte at a time:"); //read one byte at a timein =Newfileinputstream (file); intTempbyte;  while((Tempbyte=in.read ())! =-1) {System.out.write (tempbyte);   } in.close (); } Catch(IOException e) {e.printstacktrace (); return; }   Try{System.out.println ("Read the contents of the file in bytes, read multiple bytes at a time:"); //read multiple bytes at a timebyte[] Tempbytes =New byte[100]; intByteread = 0; Inch=NewFileInputStream (fileName);   Readfromfile.showavailablebytes (in); //reads in multiple bytes into a byte array, Byteread is the number of bytes read in at a time while((Byteread = In.read (tempbytes))! =-1) {System.out.write (tempbytes,0, Byteread); }   } Catch(Exception E1) {e1.printstacktrace (); } finally {   if(In! =NULL){   Try{in.close (); } Catch(IOException E1) {}}} }   /*** Read files in characters, commonly used for reading text, numbers and other types of files *@paramFileName file name*/    Public Static voidreadfilebychars (String fileName) {File file=NewFile (fileName); Reader Reader=NULL; Try{System.out.println ("reads the contents of the file in characters, one byte at a time:"); //read one character at a timeReader =NewInputStreamReader (Newfileinputstream (file)); intTempchar;  while((Tempchar = Reader.read ())! =-1){   //for Windows, the two characters of Rn, when they are together, represent a newline. //However, if the two characters are displayed separately, the lines are changed two times. //So, shield off R, or block N.   Otherwise, there will be a lot more empty rows. if(((Char) tempchar)! = ' R ') {System.out.print (Char) Tempchar);   }} reader.close (); } Catch(Exception e) {e.printstacktrace (); }   Try{System.out.println ("Read the contents of the file in characters, read multiple bytes at a time:"); //read multiple characters at onceChar[] Tempchars =New Char[30]; intCharread = 0; Reader=NewInputStreamReader (NewFileInputStream (fileName)); //Reads multiple characters into a character array, charread the number of characters to read at a time while((Charread = Reader.read (tempchars))!=-1){   //also shield off R does not showif((Charread = = tempchars.length) && (tempchars[tempchars.length-1]! = ' R ') {System.out.print (tempchars); }Else{    for(inti=0; i<charread; i++){   if(Tempchars[i] = = ' R '){   Continue; }Else{System.out.print (tempchars[i]); }   }   }   }   } Catch(Exception E1) {e1.printstacktrace (); }finally {   if(Reader! =NULL){   Try{reader.close (); } Catch(IOException E1) {}}} }   /*** Read files in behavioral units, often used to read line-oriented format files *@paramFileName file name*/    Public Static voidreadfilebylines (String fileName) {File file=NewFile (fileName); BufferedReader Reader=NULL; Try{System.out.println ("Read the contents of the file in the behavior unit and read the entire line at a time:"); Reader=NewBufferedReader (Newfilereader (file)); String tempstring=NULL; intline = 1; //read one line at a time until NULL is read to the end of the file while((tempstring = Reader.readline ())! =NULL){   //Show Line NumbersSystem.out.println ("line" + Line + ":" +tempstring); Line++;   } reader.close (); } Catch(IOException e) {e.printstacktrace (); } finally {   if(Reader! =NULL){   Try{reader.close (); } Catch(IOException E1) {}}} }   /*** Random Read file contents *@paramFileName file name*/    Public Static voidreadfilebyrandomaccess (String fileName) {randomaccessfile randomfile=NULL; Try{System.out.println ("Random reading of a file content:"); //open a random Access file stream as read-onlyRandomfile =NewRandomaccessfile (FileName, "R"); //file length, number of bytesLongFilelength =randomfile.length (); //the starting position of the read fileintBeginindex = (Filelength > 4)? 4:0; //moves the start position of the read file to the Beginindex location. Randomfile.seek (Beginindex); byte[] bytes =New byte[10]; intByteread = 0; //read 10 bytes at a time, or read the remaining bytes if the contents of the file are less than 10 bytes. //assigns the number of bytes read to Byteread while((byteread = randomfile.read (bytes))! =-1) {System.out.write (bytes,0, Byteread); }   } Catch(IOException e) {e.printstacktrace (); } finally {   if(Randomfile! =NULL){   Try{randomfile.close (); } Catch(IOException E1) {}}} }   /*** Shows the number of bytes remaining in the input stream *@paraminch*/   Private Static voidshowavailablebytes (InputStream in) {Try{System.out.println ("The number of bytes in the current byte input stream is:" +in.available ()); } Catch(IOException e) {e.printstacktrace (); }   }    Public Static voidMain (string[] args) {String fileName= "C:/temp/newtemp.txt";   Readfromfile.readfilebybytes (FileName);   Readfromfile.readfilebychars (FileName);   Readfromfile.readfilebylines (FileName);   Readfromfile.readfilebyrandomaccess (FileName); Append the content to the end of the file}} IIImportJava.io.FileWriter; Importjava.io.IOException; ImportJava.io.RandomAccessFile; /*** Append content to the end of the file*/    Public classAppendtofile {/*** A method Append file: Use Randomaccessfile *@paramFileName *@paramContent Additions*/    Public Static voidAppendmethoda (String fileName, string content) {Try {   //open a random Access file stream, read and writeRandomaccessfile Randomfile =NewRandomaccessfile (FileName, "RW"); //file length, number of bytesLongFilelength =randomfile.length (); //moves the write file pointer to the end of the file. Randomfile.seek (filelength);   Randomfile.writebytes (content);   Randomfile.close (); } Catch(IOException e) {e.printstacktrace (); }   }   /*** B method Append file: Use FileWriter *@paramFileName *@paramcontent*/    Public Static voidAppendmethodb (String fileName, string content) {Try {   //open a write file, the second parameter in the constructor true indicates that the file is written in append formFileWriter writer =NewFileWriter (FileName,true);   Writer.write (content);   Writer.close (); } Catch(IOException e) {e.printstacktrace (); }   }    Public Static voidMain (string[] args) {String fileName= "C:/temp/newtemp.txt"; String content= "New append!"; //append files by method aAppendtofile.appendmethoda (fileName, content); Appendtofile.appendmethoda (FileName,"Append end." N); //Show file ContentsReadfromfile.readfilebylines (fileName); //Append files by method BAppendtofile.appendmethodb (fileName, content); Appendtofile.appendmethodb (FileName,"Append end." N); //Show file ContentsReadfromfile.readfilebylines (fileName); }   }   

Java read-write file encyclopedia