Java reads file content in several common ways

① Random Read of file contents

② read files in behavioral units, often used to read line-oriented format files

③ read files in characters, commonly used for reading text, numbers and other types of files

④ read files in bytes, commonly used for reading binary files, slices, sounds, images, and other files

Package Com.control;

Import Java.io.BufferedReader;
Import Java.io.File;
Import Java.io.FileInputStream;
Import Java.io.FileReader;
Import java.io.IOException;
Import Java.io.InputStream;
Import Java.io.InputStreamReader;
Import Java.io.RandomAccessFile;
Import Java.io.Reader;

public class ReadFromFile {

/**
* @param args
*/
public static void Main (string[] args) {
TODO auto-generated Method Stub
String fileName = "D:/objectuser.txt";
Readfilebybytes (FileName);
Readfilebychars (FileName);
Readfilebylines (FileName);
Readfilebyrandomaccess (FileName);
}

/**
* 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)? 0:0;
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) {
}
}
}
}
/**
* 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) {
}
}
}
}

/**
* 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 ("\ n reads the contents of the file in characters, reads 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) {
}
}
}
}
/**
* 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.println (Tempbyte);
}
} catch (Exception e) {
Todo:handle exception
E.printstacktrace ();
}

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);//Good method, the first parameter is an array, the second argument is the start position, the third argument is the length
}
} catch (Exception E1) {
E1.printstacktrace ();
} finally {
if (in = null) {
try {
In.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 ();
}
}

}

Java reads file contents in several common ways