Java - FilterInputStream read() method

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Description

The Java FilterInputStream read() method reads data from an input stream. It reads one byte and returns it as an int (0-255). It returns -1 if the end of the stream (EOF) is reached.

Declaration

Following is the declaration for java.io.FilterInputStream.read() method −

public int read()

Parameters

NA

Return Value

The method returns the next byte of data, or -1 if the end of the stream is reached.

Exception

IOException − If an I/O error occurs

Example - Usage of FilterInputStream read() method

The following example shows the usage of Java FilterInputStream read() method.

FilterInputStreamDemo.java

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;
      
      try {
         // create input streams
         is = new FileInputStream("test.txt");
         fis = new BufferedInputStream(is);
         
         // read till the end of the stream
         while((i = fis.read())!=-1) {
         
            // converts integer to character
            c = (char)i;
            
            // prints
            System.out.println("Character read: "+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();
      }
   }
}

Output(assuming test.txt contains ABCDEF)

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

Character read: A
Character read: B
Character read: C
Character read: D
Character read: E
Character read: F

Example - Reading One Byte at a Time Using BufferedInputStream

The following example shows the usage of Java FilterInputStream read() method.

FilterInputStreamDemo.java

package com.tutorialspoint;

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

public class FilterInputStreamDemo {
   public static void main(String[] args) {
      try (FilterInputStream fis = new BufferedInputStream(new FileInputStream("example.txt"))) {
         int data;
         while ((data = fis.read()) != -1) { // Read byte by byte
            System.out.print((char) data); // Convert byte to char and print
         }
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output(assuming example.txt contains Hello)

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

Hello

Explanation

• Uses BufferedInputStream (a subclass of FilterInputStream).

• Reads one byte at a time using read().

• Converts byte to character ((char) data) and prints it.

• Stops when read() returns -1 (EOF).

Example - Reading Multiple Bytes into a Buffer Using PushbackInputStream

The following example shows the usage of Java FilterInputStream read() method.

FilterInputStreamDemo.java

package com.tutorialspoint;

import java.io.FileInputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.PushbackInputStream;

public class FilterInputStreamDemo {
   public static void main(String[] args) {
      try (FilterInputStream fis = new PushbackInputStream(new FileInputStream("example.txt"))) {
         byte[] buffer = new byte[5]; // Buffer to hold bytes
         int bytesRead = fis.read(buffer, 0, buffer.length); // Read multiple bytes

         System.out.println("Bytes read: " + bytesRead);
         System.out.println("Data: " + new String(buffer, 0, bytesRead)); // Convert to string
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output(assuming example.txt contains Microservices)

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

Bytes read: 5
Data: Micro

Explanation

• Uses PushbackInputStream (another FilterInputStream subclass).

• Reads up to 5 bytes into a buffer (byte[]).

• Converts bytes to string representation and prints it.