Java IO Stream

ref: http://www.studytonight.com/java/java-io-stream.php

IO Stream

Java performs I/O through Streams. A stream is linked to physical layer by java I/O system to make input and 

output operation in java. In general, a stream means continuous flow of data. Streams are clean way to deal with input/output without having every part of your code understand the physical

 

Java encapsulated Stream under java.io package. Java defined two types if stream:

1. Byte Stream:   handle input/output of byte

2. Character Stream:  handle input/output of characters. Character stream use Unicode and therefore can be internationalized

 

Byte Stream Classes

Byte Stream is defined by using two abstract class at the top of hierarchy, they are InputStream and OutputStream

 

 

## These two abstract classes have several concrete classes that handle various devices 

such as disk files, network connection etc.

 

Some important Byte stream classes:

stream class　　　　　　　　　　　　description

---------------------------------------------------------------------------------------------------------------------------------------

BufferedInputStream　　　　　　　　used for Buffered input Stream

BufferedOutputStream　　　　　　　 used for Buffered output stream

DataInputStream　　　　　　　　　　contains method for reading java standard datatype

DataOutputStream　　　　　　　　　 an output stream that contain method for writting java standard data type

FileInputStream　　　　　　　　　　　input stream that reads from a file

FileOutputStream　　　　　　　　　　 output stream that write to a file

InputStream　　　　　　　　　　　　  Abstract class that describe stream input

OutputStream　　　　　　　　　　　　Abstract class that describe stream output

PrintStream　　　　　　　　　　　　　output stream that contain print() and println() mehod

 

The above classes define several key methods. Two most important are:

read(): read byte of data

write(): write byte data

 

***************************************************************************

 

Character Stream Classes

character stream is also defined by using two abstract class at the top of hierarchy, that are Reader and writer 

These two abstract classes have several  concrete classes that handle unicode character

 

stream class　　　　　　　　　　　　description

---------------------------------------------------------------------------------------------------------------------------------------

BufferedReader　　　　　　　　　　　　handles buffered input stream　　　　　　　　

BufferedWriter　　　　　　　 　　　　　handles buffered output stream

InputStreamReader　　　　　　　　　  input stream that translate byte to character

OutputStreamWriter　　　　　　　　　 output stream that translate character to byte

FileReader　　　　　　　　　　　　　　  input stream reads from file　

FileWriter　　　　　　　　 　　　　　　  output stream that writes to file

Reader　　　　　　　　　　　　             abstract class that define character stream input

Writer　　　　　　　　　　　　　　　　　abstract class that define character stream output

PrintWriter　　　　　　　　　　　　　     output stream that contain print() and println() method

 

Reading Console Input

we use BufferedReader class obj to read inputs from keyboard

`` BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

 

Reading Characters

read() method is used with BufferedReader object to read characters. As this function returns integer type

we need to use typecasting to convert it to char type

`` int read() throws IOException

class CharRead
{
 public static void main( String args[])
 {
  BufferedReader br = new Bufferedreader(new InputstreamReader(System.in));
  char c = (char)br.read();       //Reading character  
 }
}

Reading Strings

readLine() function with BufferedReader class

`` String readLine() throw IOException

`` String line = br.readLine();

import java.io.*;
class MyInput
{
 public static void main(String[] args)
 {
  String text;
  InputStreamReader isr = new InputStreamReader(System.in);
  BufferedReader br = new BufferedReader(isr);
  text = br.readLine();          //Reading String  
  System.out.println(text);
 }
}

 

 

Program to read from a file using BufferedReader class

import java. Io *;
class ReadTest
{
 public static void main(String[] args)
 {
  try 
  {
   File fl = new File("d:/myfile.txt");
   BufferedReader br = new BufferedReader(new FileReader(fl)) ;
   String str;
   while ((str=br.readLine())!=null)
   {
    System.out.println(str);
   }
   br.close();
   fl.close();
  }
  catch (IOException  e)
  { e.printStackTrace(); }
 }

 

Program to write to a File using FileWriter class

import java. Io *;
class WriteTest
{
 public static void main(String[] args)
 {
  try 
  {
   File fl = new File("d:/myfile.txt");
   String str="Write this string to my file";
   FileWriter fw = new FileWriter(fl) ;
   fw.write(str);
   fw.close();
   fl.close();
  }
  catch (IOException  e)
  { e.printStackTrace(); }
 }
}