Java-read data from files and java reads data

Java-read data from files and java reads data

1. FileInputStream ()

// Construct a byte input stream object. The parameter is the file name FileInputStream fin = new FileInputStream ("message"); System. out. println ("number of bytes that can be read from the input stream:" + fin. available (); // create byte array B. The data read from the input stream is temporarily stored in byte B [] = new byte [fin. available ()]; // read data from the input stream fin. read (B); String str5 = new String (B); System. out. println (str5); // close the input stream. For file operations, you must close the input/output stream fin at the end. close ();

2. RandomAccessFile ()

              String str6="";              ArrayList<String> strs=new ArrayList<String>();              RandomAccessFile file=new RandomAccessFile("message","r");              str6 = file.readLine();              while(str6!=null){                  strs.add(str6);                  str6 = file.readLine();              }              for(int j=0;j<strs.size();j++){                  System.out.println(strs.get(j));              }              file.close();

3. File

File file2 = new File ("message"); if (file2.exists () & file2.isFile () {InputStream is = new FileInputStream (file2 ); byte [] buf = new byte [is. available ()]; System. out. println (is. available (); while (is. read (buf )! =-1) {// print System. out. println (new String (buf) each read ));}}

4. Avoid garbled characters

File file3 = new File ("message"); if (file3.exists () & file3.isFile () {try {InputStream is = new FileInputStream (file3 ); inputStreamReader reader = new InputStreamReader (is, "UTF-8"); // char [] cbuf = new char [is. available ()]; // character, byte StringBuffer sb2 = new StringBuffer (); // 2 while (reader. read (cbuf )! =-1) {sb2.append (cbuf);} System. out. println (sb2.toString ();} catch (Exception e ){}}

5. BufferedReader

            File file = new File("message");            try {                InputStream is = new FileInputStream(file);                if (file.exists() && file.isFile()) {                    BufferedReader br = new BufferedReader(                            new InputStreamReader(is, "utf-8"));                    StringBuffer sb2 = new StringBuffer();                    String line = null;                    while ((line = br.readLine()) != null) {                        sb2.append(line + "\n");                    }                    br.close();                    System.out.println(sb2.toString());                }            } catch (Exception e) {            }

 

The best code for writing files and reading data from files in Java!

Import java. io. BufferedReader;
Import java. io. File;
Import java. io. FileReader;
Import java. io. FileWriter;
Import java. io. IOException;

Public class IOTest {

Public static void main (String [] args ){
String str = "123 \ r \ n456 ";
WriteFile (str); // write
String str1 = readFile (); // read
System. out. println (str1 );
}

/**
* Pass written content
* @ Param str
*/
Static void writeFile (String str ){
Try {
File file = new File ("d: \ file.txt ");
If (file. exists () {// exists
File. delete (); // delete and recreate
File. createNewFile ();
} Else {
File. createNewFile (); // directly created if the file does not exist
}
FileWriter fw = new FileWriter (file); // file write IO
Fw. write (str );
Fw. flush ();
Fw. close ();
} Catch (IOException e ){
E. printStackTrace ();
}
}

/**
* Returned read content
* @ Return
*/
Static String readFile (){
String str = "", temp = null;
Try {
File file = new File ("d: \ file.txt ");
FileReader fr = new FileReader (file );
BufferedReader br = new BufferedReader (fr); // File Read IO
While (temp = br. readLine ())! = Null) {// until the end of reading
Str + = (temp + "\ n ");
}
Br. close ();
Fr. close ();
} Catch (IOException e ){
E. printStackTrace ();
}
Return str;
}
}

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How to read data from a file in java

It can be divided into two types: Read byte and read character.
◎ FileInputStream byte input stream Read File ◎
Public class Maintest {

Public static void main (String [] args) throws IOException {

File f = new File ("G: \ just for fun \ xiangwei.txt ");

FileInputStream fin = new FileInputStream (f );

Byte [] bs = new byte [1024];

Int count = 0;
While (count = fin. read (bs)> 0)
{

String str = new String (bs, 0, count); // define new variables repeatedly: each time a new variable is redefined, it receives new read data.

System. out. println (str); // output new variables repeatedly: each time a new variable is output
}
Fin. close ();
}
}

◎ FileReader character input stream Read File ◎
Public class Maintest {
Public static void main (String [] args) throws IOException {

File f = new File ("H: \ just for fun \ xiangwei.txt ");

FileReader fre = new FileReader (f );

BufferedReader bre = new BufferedReader (fre );

String str = "";
While (str = bre. readLine ())! = Null) // ● determines whether the last row does not exist. It is null.
{
System. out. println (str );
}
Bre. close ();
Fre. close ();

}

}