Java IO

JAVA STREAM CLASS REPRESENTATION

Input -- Reading content
Output -- writing the content

Java stream class are of two type
1. Byte Stream - for I/O on bytes
2. Character Stream - for I/O operation on character

Character Stream Class	Byte Stream Class
Reader	Input stream
Buffered Reader	Buffered input stream
Buffered Writer	Buffered output stream
File reader	File input stream
File writer	File output stream

What is Stream?

Input stream/ output stream is the way of reading and writing raw data respectively. In stream, data are read byte by byte. For example if you want to read an image file or a binary file use Byte Stream Class
Where character stream is used for reading all text. It takes care of character decoding to give Unicode character.

What is Buffer and Un-buffered ?

Unbuffered I/O - For unbuffered access read and write operation is handled by Operating System level. Unbuffered way of reading and writing files involves direct disk access. Which is inefficient in terms of performance.

Buffered I/O - To overcome the inefficiency the way read and write operation occurs for unbuffered  way buffered stream is used. In buffered stream read operation is performed on memory. The memory is nothing but what we call buffer. native API is called when buffer is empty. Write operation is also performed on memory i.e. buffer, when the buffer is full native API is called

Unbuffered stream can be converted to buffer stream in following ways

For character class

inputStream = new BufferedReader(new FileReader("xanadu.txt"));
outputStream = new BufferedWriter(new FileWriter("characteroutput.txt"));

 //Read File Using Buffered input stream   

 package example1;   
  import java.io.BufferedInputStream;   
  import java.io.FileInputStream;   
  import java.io.FileNotFoundException;   
  import java.io.IOException;   
  public class FileReader {   
    public static void main(String[] args) {   
       reader r = new reader();   
       r.fileReader();   
    }   
  }   
  class reader {   
    public void fileReader() {   
       // this constructor accept a input stream   
       try {   
         BufferedInputStream bis = new BufferedInputStream(   
              new FileInputStream("C:/Test/sudas.txt"));   
         while (bis.available() > 0) {   
            int read = bis.read();   
            System.out.print((char) read);   
         }   
       } catch (IOException e) {   
         // TODO Auto-generated catch block   
         e.printStackTrace();   
       }   
    }   
  }   

 // Write File Using BufferedOutputStream   

 Class BufferOutput   
  {   
    public void bufferout()   
    {   
       try {   
         BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("C:/Test/File1.txt"));   
         String sample="This is a sample text";   
         byte[] inbyte = sample.getBytes();   
         bos.write(inbyte);   
         bos.flush();   
         bos.close();   
       } catch (IOException e) {   
         // TODO Auto-generated catch block   
         e.printStackTrace();   
       }   
    }   
  }   

 //Read File Using Buffered Reader  using READLINE method

 package example1;   
  import java.io.BufferedReader;   
  import java.io.IOException;   
  public class FileReader {   
    public static void main(String[] args) {   
       reader r = new reader();   
       r.fileReader();   
    }   
  }   
  class reader {   
    // "C:/Test/sudas.txt"   
    public void fileReader() {   
       try {   
         BufferedReader reader = new BufferedReader(new java.io.FileReader(   
              "C:/Test/sudas.txt"));   
         while (reader.readLine() != null) {   
            String read = reader.readLine();   
            System.out.println(read);   
         }   
       } catch (IOException e) {   
         // TODO Auto-generated catch block   
         e.printStackTrace();   
       }   
    }   
  }   

// Use of Buffer Reader using READ method

      public static void readCookies(String filePath) throws IOException {  
           BufferedReader br = new BufferedReader(new FileReader(new File(filePath)));  
           int line;  
           while((line=br.read())!=-1)  
           {  
           System.out.println((char)line);       
           }  
      }  

  //Write file using BufferedWriter   

  public void writer() {   
       String path = "C:/Test/CreateFile.txt";   
       // create a file   
       File file = new File(path);   
       try {   
         if (file.exists()) {   
            file.deleteOnExit();   
            System.out.println("file exists deleting file");   
         }   
         else {   
            file.createNewFile();   
         }   
         BufferedWriter writer = new BufferedWriter(new FileWriter(path));   
         writer.write("This is for Test Purpose");   
         writer.flush();   
         writer.close();   
       } catch (IOException e) {   
         // TODO Auto-generated catch block   
         e.printStackTrace();   
       }   
    }   

 // EXAMPLE TO CREATE FILE, IF EXISTS DELETE FILE  

    public void writer() {   
       String path = "C:/Test/CreateFile.txt";   
       // create a file   
       File file = new File(path);   
       try {   
         if (file.exists()) {   
            file.deleteOnExit();   
            System.out.println("file exists deleting file");   
         }   
         else {   
            file.createNewFile();   
         }   
         // BufferedWriter writer = new BufferedWriter(new FileWriter(path));   
       } catch (IOException e) {   
         // TODO Auto-generated catch block   
         e.printStackTrace();   
       }   
    }   

  // Utility to copy the content of one file to the other   

  class CopyContent {   
    public void copy() {   
       String sourceFile = "C:/Test/AdobeARM.log";   
       String destinationFile = "C:/Test/CreateFile.txt";   
       try {   
         // create a file   
         File file = new File(destinationFile);   
         if (file.exists()) {   
            file.deleteOnExit();   
            System.out.println("file exists deleting file");   
         } else {   
            file.createNewFile();   
            System.out.println("File created");   
         }   
         // Read the source file content   
         BufferedReader breader = new BufferedReader(new java.io.FileReader(   
              new File(sourceFile)));   
         BufferedWriter writer = new BufferedWriter(new FileWriter(   
              destinationFile));   
         while (breader.readLine() != null) {   
            char[] readLine = breader.readLine().toCharArray();   
            // write   
            writer.write(readLine);   
            writer.write('\n');   
         }   
         writer.close();   
       } catch (IOException e) {   
         // TODO Auto-generated catch block   
         e.printStackTrace();   
       }   
    }   
  }   

This is an example to get String from Fileinputstream using StringBuilder

 class LogScanner {  
      public void scan() {  
           // fileinputstream to string  
           StringBuilder sb = new StringBuilder();  
           try {  
                FileInputStream fis = new FileInputStream(new File("/Users/S_Das/Documents/Java/sudas.log"));  
                int input;  
                while((input = fis.read())!=-1){  
                sb.append((char)input);  
                }  
                System.out.println(sb.toString());  
                fis.close();  
           } catch (IOException e) {  
                // TODO Auto-generated catch block  
                e.printStackTrace();  
           }  
      }  
 }