I/O

Class InputStream

• It represents input stream of bytes i.e. a flow of bytes from which we can read data.
• It will read data from file or device or remote system.
• It is an abstract class.

• int read()
• It reads next byte of data from the input stream.
• For ex:
int ch=in.read();
• int read( byte[ ] buffer )
• it reads buffer.length bytes and stores them into the buffer.
• It returns no. of bytes actually read.
• For ex:

                  byte arr[]=new byte[100];
                  n=in.read(arr);

• int read( byte[ ] buffer , int off, int len)
• It reads len no. of bytes and stores it into an buffer array at offset position.
• For ex:

                  byte arr[]=new byte[100];
                  n=in.read(arr,25,50);

Note:the above methods will returns -1 at end of stream.
• int available()
• It returns the number of bytes that can be read from stream.
• For ex:
int n=in.available();
• void close()
• This method closes this input stream.

Class FileInputStream

• It is used read bytes from a file.
• It is derived from class InputStream.

• FileInputStream(String name)
  • Creates a new FileReader, given the name of the file to read from.
  • For ex:
  FileReader dr=new FileReader("c:/temp/demo.txt");
• FileInputStream(File file)
• Will creates a FileInputStream to read data from file.
• If file is not present it will throw an exception.
• For ex:

                File fa=new File("c:/temp/demo.txt");
                FileInputStream fin=new FileInputStream(fa);

 import java.io.*;
 class demo
 {
    public static void main(String[ ] args) 
   {
	    try{
     	  FileInputStream fin=new FileInputStream("c:\\temp\\info.txt");
	      int ch;
	      while((ch=fin.read())!=-1)
		      System.out.print((char)ch);
	      fin.close();
	    }
	    catch(Exception err)
		  {
		    System.out.println("ERROR:"+err);
		  }
   }
 }

Welcome to CCIT
Amravati

Class OutputStream

• It represents a flow of bytes in which we can write data.
• By using OutputStream data may be send to a file or device or remote system
• It is an abstract class.

• void write(int b)
• it writes the specified byte to this output stream.
• For ex:
out.write(ch);
• void write(byte[] buffer)
• it writes buffer.length bytes from the specified byte array to output stream.
• For ex:
out.write(arr);
• void write(byte[] buffer, int off, int len)
• it writes len bytes from the specified byte array starting at offset to output stream.
• For ex:
out.write(arr,25,50);
• void close()
• it closes this output stream and releases any system resources associated with this stream.

Class FileOutputStream

• It is used for writing data to a file.
• It is derived from class OutputStream.

• FileOutputStream(String name)
• FileOutputStream(File file)
• It creates an FileOutputStream to write data into the file.
• If file is present it is overwrittern else new file is created.
• For ex:

                FileOutputStream fout=new FileOutputStream(“c:/temp/demo.txt”);
                Or
                File fa=new File(“c:/temp/demo.txt”);
                FileOutputStream fout=new FileOutputStream(fa);
        

• FileOutputStream(String name, boolean append)
• FileOutputStream(File file, boolean append)
• Will create a FileOutputStream object to write data into file.
• If append (true) is passed then data will be added at end.
• If append (false) is passed then file will be overwritten if present.

 import java.io.*;
 class demo
 {
    public static void main(String[ ] args) throws Exception
    {
     	FileWriter fw=new FileWriter("c:\\temp\\myinfo.txt");
	    fw.write("P.Choudhari");
	    fw.write("\nCCIT\nRajapeth\nAmravati");
	    fw.close();
    }
 }