Java Read File Method encyclopedia _java

1, read the contents of the file by byte

public class ReadFromFile {public

static void Readfilebybytes (String fileName) {
file File = new File (fileName); C3/>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 time in
= new FileInputStream (file);
int tempbyte;
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 time
byte[] tempbytes = new byte[100];
int byteread = 0;
in = new FileInputStream (fileName);
Readfromfile.showavailablebytes (in);
Reads multiple bytes into a byte array, byteread the number of bytes read in while
(Byteread = In.read (tempbytes))!=-1) {
System.out.write ( Tempbytes, 0, Byteread);
}
catch (Exception E1) {
e1.printstacktrace ();
} finally {
if (in!= null) {
try {
in.close (); c34/>} catch (IOException E1) {
}}}

2, read the contents of the file by character

public static void Readfilebychars (String filename) {File File = new file (fileName);
Reader reader = null; try {System.out.println (read the contents of the file in characters, one byte at a time:);//read one character reader = new InputStreamReader (new FileInputStream (file))
;
int Tempchar;
while ((Tempchar = Reader.read ())!=-1) {//for Windows, \ r \ n These two characters together indicate a newline.
However, if the two characters are displayed separately, the lines will be changed two times. So, block \ r, or block \ n.
Otherwise, there will be a lot more empty lines.
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 once char[] tempch
ARS = new CHAR[30];
int charread = 0;
reader = new InputStreamReader (fileName) (new FileInputStream); Reads more than one character into an array of characters, charread as the number of read characters while (Charread = Reader.read (tempchars))!=-1) {//also shielded \ r does not display if (Charread = tempch Ars.length) && (tempchars[tempchars.length-1]!= ' \ R ')) {System.out.print (tempchars);} else {for (int i = 0; i < Charread; i++) {if (tempchars[i] = = ' \ r ') {continue} ElSE {System.out.print (tempchars[i]);} {E1.printstacktrace ()}} catch (Exception E1) {()} finally {if (reader!= null) {try {reader.close ();} catch (Ioexc Eption E1) {}}}}

3, read the contents of the file by line

public static void Readfilebylines (String filename) {
File File = new file (fileName);
BufferedReader reader = null;
try {
System.out.println ("reads the contents of the file in a unit of behavior, reads one whole line at a time:");
reader = new BufferedReader (new FileReader (file));
String tempstring = null;
int line = 1;
Read one row at a time until you read null for file end while
((tempstring = Reader.readline ())!= null) {
//Show line number
System.out.println (" Line "+ line +": "+ tempstring";
line++;
}
Reader.close ();
} catch (IOException e) {
e.printstacktrace ();
} finally {
if (reader!= null) {
try {
Reader.close ();
} catch (IOException E1) {
}}}

4, Random Read the contents of the file

public static void Readfilebyrandomaccess (String fileName) {randomaccessfile randomfile = null; try {SYSTEM.OUT.PRINTLN
("read the contents of a document randomly:");
Open a random Access file stream, read-only randomfile = new Randomaccessfile (FileName, "R");
File length, byte number long filelength = Randomfile.length (); Read the starting position of the file int beginindex = (Filelength > 4)?
4:0;
Moves the start position of the read file to the Beginindex location.
Randomfile.seek (Beginindex);
byte[] bytes = new BYTE[10];
int byteread = 0;
Read 10 bytes at a time and read the remaining bytes if the file content is less than 10 bytes. Assigns a read number of bytes 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 (Ioex Ception E1) {}}}} private static void Showavailablebytes (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 void Main (string[] args) {String fileName = ' c:/temp/newtemp.txt '; Readfromfile.readfilebybytes(FileName);
Readfromfile.readfilebychars (FileName);
Readfromfile.readfilebylines (FileName);
Readfromfile.readfilebyrandomaccess (FileName); }
}

5, append content to file tail

public class Appendtofile {public static void Appendmethoda (string fileName, string content) {try {//Open a random Access file stream, read/write
The way randomaccessfile randomfile = new Randomaccessfile (fileName, "RW");
File length, byte number long filelength = 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 ();}}  public static void Appendmethodb (string fileName, string content) {try {//Open a write-file, the second argument in the constructor is true to write the file in append form FileWriter
writer = new FileWriter (FileName, true);
Writer.write (content);
Writer.close ();

catch (IOException e) {e.printstacktrace ();}}
public static void Main (string[] args) {String fileName = ' c:/temp/newtemp.txt ';
String content = "New append!";
Append file Appendtofile.appendmethoda (filename, content) by method A; Appendtofile.appendmethoda (FileName, "append end.")
\ n ");
Displays the contents of the file Readfromfile.readfilebylines (fileName);
Append file Appendtofile.appendmethodb (filename, content) by method B; Appendtofile.appenDmethodb (FileName, "append end.")
\ n ");
Displays the contents of the file Readfromfile.readfilebylines (fileName); }
}