Java file reading Daquan

In this I only collected four kinds of file reading methods, namely: Read the contents of the file by byte, read the contents of the file by character, read the contents of the file by the line, read the contents of the file randomly, and append the contents to the file;

Needless to say, direct sticker code, hope to help some people! If there is no understanding can add me QQ592652578, detailed chat.

public class ReadFromFile {

1. read file contents by byte
/**
* Read files in bytes, often used to read binary files, slices, sounds, images, and other files.
*/
public static void Readfilebybytes (String fileName) {
File File = new file (fileName);


InputStream in = null;
try {
System.out.println ("read 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 more than one byte 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 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) {


}
}
}
}

2.read file contents by character
/**
* Read files in characters, commonly used for reading text, numbers and other types of files
*/
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 at a time
reader = new InputStreamReader (new FileInputStream (file));
int Tempchar;
while ((Tempchar = Reader.read ())! =-1) {
For Windows, \ r \ n These two characters are together, representing a newline.
However, if the two characters are displayed separately, the lines are changed two times.
Therefore, block \ 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 once
char[] Tempchars = new CHAR[30];
int charread = 0;
reader = new InputStreamReader (new FileInputStream (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 show
if ((Charread = = tempchars.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]);
}
}
}
}


} catch (Exception E1) {
E1.printstacktrace ();
} finally {
if (reader! = null) {
try {
Reader.close ();
} catch (IOException E1) {
}
}
}
}


3. read file contents by line
/**
* Read files in behavioral units, often used to read line-oriented format files
*/
public static void Readfilebylines (String fileName) {
File File = new file (fileName);
BufferedReader reader = null;
try {
System.out.println ("read the contents of the file in the Act unit, read a whole line at a time:");
reader = new BufferedReader (new FileReader (file));
String tempstring = null;
int line = 1;
Read one line at a time until NULL is read to the end of the file
while ((tempstring = Reader.readline ()) = null) {
Show line Numbers
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 reading of file contents
/**
* Random reading of file contents
*/
public static void Readfilebyrandomaccess (String fileName) {
Randomaccessfile randomfile = null;
try {
System.out.println ("Random reading of a file content:");
Open a random Access file stream as read-only
Randomfile = new Randomaccessfile (FileName, "R");
File length, number of bytes
Long filelength = Randomfile.length ();
The starting position of the read 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, 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
*/
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 the file
public class Appendtofile {
/**
* A method Append file: Use Randomaccessfile
*/
public static void Appendmethoda (string fileName, string content) {
try {
Open a random Access file stream, read and write
Randomaccessfile randomfile = new Randomaccessfile (fileName, "RW");
File length, number of bytes
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 ();
}
}


/**
* B method Append file: Use FileWriter
*/
public static void Appendmethodb (string fileName, string content) {
try {
Open a write file, the second parameter in the constructor true indicates that the file is written 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 files by Method a
Appendtofile.appendmethoda (fileName, content);
Appendtofile.appendmethoda (FileName, "append end. \ n ");
Show file contents
Readfromfile.readfilebylines (FileName);
Append files by Method b
Appendtofile.appendmethodb (fileName, content);
Appendtofile.appendmethodb (FileName, "append end. \ n ");
Show file contents
Readfromfile.readfilebylines (FileName);
}
}

Java file reading Daquan