java--byte stream, character stream

one, byte output streamOutputStream Abstract class

This abstract class is a superclass of all classes that represent the output byte stream. The data of operation is byte, and the basic common function method of output byte stream is defined.

• BYTE: This stream only operates 1 bytes in the file at a time
• Stream object: When you manipulate files, you do not rely on the operating system

Function: From Java program, write file (can write arbitrary file)

Method:

• Write (int b) writes 1 bytes
• Write (byte[] b) writes a byte array
• Write (byte[] b,int,int) writes a byte array, int begins to write the index, and int writes several
• Close () method, closes the stream object, frees the resources associated with this stream

FileOutputStream class

OutputStream has many subclasses, where subclasses FileOutputStream can be used to write data to a file.

The FileOutputStream class, the file output stream, is the output stream used to write data to file .

Flow object Use steps:

• 1. Create an object of the stream subclass, bind the data purpose
• 2. Calling the Stream object's method write
• 3. Close Releases resources

1. Writing Files

public static void Main (string[] args) throws IOException {//Stream object construction method, you can create a file if the file exists, directly overwrite fileoutputstream fos = new FileOutputStream ("C:\\a.txt");//The method of the Stream object write writes data//write 1 bytes, query the encoding table Fos.write (97);//write byte array byte[] bytes = {65,66,67,68}; Fos.write (bytes);//write a part of the byte array, start the index, write a few fos.write (bytes, 1, 2);//write the byte array in a convenient way//writes the string fos.write ("Hello". GetBytes ());// Close resource Fos.close ();}

2. Exception handling of IO stream

Import Java.io.fileoutputstream;import java.io.ioexception;/* *   exception handling for IO stream *   Try Catch finally *    *   Details: *     1. Guaranteed Flow object variable, scope sufficient *     2. Catch inside, how to deal with exceptions *         output abnormal information, the purpose to see where the problem *         Stop the program, new try *     3. If the stream object fails to build, do you need to close the resource? * The         new object failed with no system resources *         when releasing the resource, the convection object determines that the null *         variable is not NULL, the object is established successfully, and the resource needs to be closed */public class FileOutputStreamDemo3 {public static void main ( String[] args) {//try outside declares the variable, the try inside establishes the object FileOutputStream fos = Null;try{fos = new FileOutputStream ("S:\\a.txt"); fos.write (100);} catch (IOException ex) {System.out.println (ex); throw new RuntimeException ("File write failed, retry");} Finally{try{if (fos!=null)      fos.close ();} catch (IOException ex) {throw new RuntimeException ("Close resource Failed");}}}

3. The string is converted into a byte array

"Hello,world!". getBytes ()

4, the document continues to write

FileOutputStream fos = new FileOutputStream (file, true);

second, byte input streamInputStream Abstract class

Can be achieved by InputStream. InputStream this abstract class, which is a superclass of all classes that represent the byte input stream. , the basic common function method of byte input stream is defined.

• int Read (): reads a byte and returns, no bytes returned -1.

• int Read (byte[]): reads a certain amount of bytes and stores it in a byte array, returning the number of bytes read to, no bytes returned -1.

FileInputStream class

To read a file from an input stream

• 1. Create a subclass object for the byte input stream
• 2. Call reading method Read Read
• 3. Close Resources

Read () method,

• Read () executes once and automatically reads the next byte
• The return value, which is the read-from byte, is returned to the end of the read-1

1. Read a single byte

public static void Main (string[] args) throws Ioexception{fileinputstream fis = new FileInputStream ("C:\\a.txt");//  Reads a byte, calls the method read returns int//using the loop, reads the file, the  loop ends the condition that the  read () method returns -1int len = 0;//accepts the return value of the Read method while (len = Fis.read ())! = -1) {//return value saved to Len System.out.print ((char) len);} Close resource Fis.close ();}

2. Read an array of bytes

public static void Main (string[] args) throws IOException {FileInputStream fis = new FileInputStream ("C:\\a.txt");//number of bytes created Group byte[] B = new Byte[1024];int len = 0; while (len = Fis.read (b))!=-1) {//save to byte array b System.out.print (new String (B,0,len ));} Fis.close ();}

Copy File

public static void Main (string[] args) {long s = system.currenttimemillis (); FileInputStream FIS = null; FileOutputStream fos = Null;try{fis = new FileInputStream ("C:\\t.zip"); fos = new FileOutputStream ("D:\\t.zip");//define byte array , buffer byte[] bytes = new byte[1024*10];//read array, write array int len = 0; while (len = fis.read (bytes))!=-1) {fos.write (bytes, 0, Len);}} catch (IOException ex) {System.out.println (ex); throw new RuntimeException ("File copy Failed");} Finally{try{if (Fos!=null) Fos.close ();} catch (IOException ex) {throw new RuntimeException ("Release resource Failed");} Finally{try{if (Fis!=null) Fis.close ();} catch (IOException ex) {throw new RuntimeException ("Release resource Failed");}}} Long e = System.currenttimemillis (); System.out.println (e-s);}

three, character input/output stream

1, character input--filereader class

The character input stream can only read a text file, and the superclass of all character input streams is the Java.io.Reader class

• int read () reads 1 characters
• int read (char[] c) Read character array

public static void Main (string[] args) throws Ioexception{filereader fr = new FileReader ("C:\\1.txt");//Read single character/*int len = 0; while (len = Fr.read ())!=-1) {System.out.print ((char) len);} *///character array char[] ch = new Char[1024];int len = 0; while (len = Fr.read (ch))!=-1) {System.out.print (new String (Ch,0,len));} Fr.close ();}

2, character output stream--filewriter

The superclass of all character output streams is Java.io.Writer

• Write (int c) writes 1 characters
• Write (char[] c) An array of uppercase characters
• Write (char[] c,int,int) character array, start index, write a few
• Write (string s) writes a string

public static void Main (string[] args) throws Ioexception{filewriter fw = new FileWriter ("C:\\1.txt");//write 1 characters fw.write ( Fw.flush ();//write 1-character array char[] C = {' A ', ' B ', ' C ', ' d ', ' E '};fw.write (c); Fw.flush ();//write character array part fw.write (C, 2, 2); Fw.flush ();//write String fw.write ("Hello"); Fw.flush (); Fw.close ();}

Copy File

public static void Main (string[] args) {FileReader FR = null; FileWriter FW = NULL;TRY{FR = new FileReader ("C:\\1.txt"), FW = new FileWriter ("D:\\1.txt"); char[] Cbuf = new Char[1024];in T len = 0; while (len = Fr.read (cbuf))!=-1) {fw.write (cbuf, 0, Len); Fw.flush ();}} catch (IOException ex) {System.out.println (ex); throw new RuntimeException ("Copy Failed");} Finally{try{if (Fw!=null) Fw.close ();} catch (IOException ex) {throw new RuntimeException ("Release resource Failed");} Finally{try{if (Fr!=null) Fr.close ();} catch (IOException ex) {throw new RuntimeException ("Release resource Failed");}}}

java--byte stream, character stream