Java.io.FilterInputStream.read() Method

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Description

The java.io.FilterInputStream.read(byte[] b, int off, int len) method reads up to len of data from this filter input stream into a buffer.

Declaration

Following is the declaration for java.io.FilterInputStream.read(byte[] b, int off, int len) method −

public int read(byte[] b, int off, int len)

Parameters

• b − The destination buffer.

• off − The start offset in the destination buffer.

• len − The maximum number of bytes read.

Return Value

The method returns the total number of bytes read into the buffer, or -1 if there is no more data to read.

Exception

• IOException − If an I/O error occurs.

• IndexOutOfBoundsException − If len is greater that b.length-off, if off is negative, or if len is negative.

• NullPointerException − If buffer b is null.

Example

The following example shows the usage of java.io.FilterInputStream.read(byte[] b, int off, int len) method.

package com.tutorialspoint;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

public class FilterInputStreamDemo {
   public static void main(String[] args) throws Exception {
      InputStream is = null; 
      FilterInputStream fis = null;
      int i = 0;
      char c;
      byte[] buffer = new byte[6];
      
      try {
         // create input streams
         is = new FileInputStream("C://test.txt");
         fis = new BufferedInputStream(is);
         
         // returns number of bytes read to buffer
         i = fis.read(buffer, 2,4);
         
         // prints
         System.out.println("Number of bytes read: "+i);
         
         // for each byte in buffer
         for(byte b:buffer) {
         
            // converts byte to character
            c = (char)b;
            
            // if byte is null
            if(b == 0)
               c = '-';
            // prints
            System.out.println("Char read from buffer b: "+c);
         }
         
      } catch(IOException e) {
         // if any I/O error occurs
         e.printStackTrace();
      } finally {
         // releases any system resources associated with the stream
         if(is!=null)
            is.close();
         if(fis!=null)
            fis.close();
      }
   }
}

Assuming we have a text file c:/test.txt, which has the following content. This file will be used as an input for our example program −

ABCDEF

Let us compile and run the above program, this will produce the following result −

Number of bytes read: 4
Char read from buffer b: -
Char read from buffer b: -
Char read from buffer b: A
Char read from buffer b: B
Char read from buffer b: C
Char read from buffer b: D