DataInputStream readByte() method in Java with Examples

The readByte() method of DataInputStream class in Java is used to read and return one input byte. The byte is a signed value in the range from -128 to +127. The bytes in this method are read from the accommodated input stream.

Syntax:

public final byte readByte()
                  throws IOException

Specified By: This method is specified by readByte() method of DataInput interface.

Parameters: This method does not accept any parameter.

Return value: This method returns the byte value read. It is a signed 8-bit byte.

Exceptions:

• EOFException – It throws EOFException if the input stream is ended.
• IOException – This method throws IOException if the stream is closed or some other I/O error occurs.

Below programs illustrate readByte() method in DataInputStream class in IO package:

Program 1:

// Java program to illustrate
// DataInputStream readByte() method
import java.io.*;
public class GFG {
    public static void main(String[] args)
        throws IOException
    {

        // Create byte array
        byte[] b = { 10, 20, 30, 40, 50 };

        // Create byte array input stream
        ByteArrayInputStream byteArrayInputStr
            = new ByteArrayInputStream(b);

        // Convert byte array input stream to
        // DataInputStream
        DataInputStream dataInputStr
            = new DataInputStream(
                byteArrayInputStr);

        while (dataInputStr.available() > 0) {
            // Print bytes
            System.out.println(
                dataInputStr.readByte());
        }
    }
}

Output:

10
20
30
40
50

Program 2:

// Java program to illustrate
// DataInputStream readByte() method
import java.io.*;
public class GFG {
    public static void main(String[] args)
        throws IOException
    {

        // Create byte array
        byte[] b = { -20, -10, 0, 10, 20 };

        // Create byte array input stream
        ByteArrayInputStream byteArrayInputStr
            = new ByteArrayInputStream(b);

        // Convert byte array input stream to
        // DataInputStream
        DataInputStream dataInputStr
            = new DataInputStream(
                byteArrayInputStr);

        while (dataInputStr.available() > 0) {
            // Print bytes
            System.out.println(
                dataInputStr.readByte());
        }
    }
}

Output:

-20
-10
0
10
20

References:
https://docs.oracle.com/javase/10/docs/api/java/io/DataInputStream.html#readByte()