Java - InputStream read() method

---

---

Description

The Java InputStream read() method reads the next byte of the data from the the input stream and returns int in the range of 0 to 255. If no byte is available because the end of the stream has been reached, the returned value is -1.

Declaration

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

public abstract int read()

Parameters

NA

Return Value

This 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 InputStream read() method

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

InputStreamDemo.java

package com.tutorialspoint;

import java.io.FileInputStream;
import java.io.InputStream;

public class InputStreamDemo {
   public static void main(String[] args) throws Exception {
      InputStream is = null;
      int i;
      char c;
      
      try {
         // new input stream created
         is = new FileInputStream("test.txt");
         
         System.out.println("Characters printed:");
         
         // reads till the end of the stream
         while((i = is.read())!=-1) {
         
            // converts integer to character
            c = (char)i;
            
            // prints character
            System.out.print(c);
         }
         
      } catch(Exception e) {
         // if any I/O error occurs
         e.printStackTrace();
      } finally {
         // releases system resources associated with this stream
         if(is!=null)
            is.close();
      }
   }
}

Output(Assuming test.txt contains "ABCDE")

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

Characters printed:
ABCDE

Example - Reading One Byte at a Time Using FileInputStream

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

InputStreamDemo.java

package com.tutorialspoint;

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

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

Output(if example.txt contains "Hello")

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

Hello

Explanation

• Uses FileInputStream, a subclass of InputStream, to read "example.txt".

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

• Converts the integer ASCII/Unicode value to a character((char) data) and prints it.

• Stops when read() returns -1 (EOF reached).

Example - Reading One Byte at a Time Using ByteArrayInputStream

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

InputStreamDemo.java

package com.tutorialspoint;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;

public class InputStreamDemo throws IOException {
   public static void main(String[] args) {
      byte[] data = "Java".getBytes(); // Convert string to byte array
      InputStream inputStream = new ByteArrayInputStream(data);

      int byteRead;
      while ((byteRead = inputStream.read()) != -1) { // Read one byte at a time
         System.out.print((char) byteRead);
      }

      try {
         inputStream.close();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output

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

Java

Explanation

• Uses ByteArrayInputStream, which works with byte arrays instead of files.

• Converts the string "Java" to bytes ("Java".getBytes()).

• Reads one byte at a time and prints the character.

• Closes the stream manually to free memory.