DataInputStream readDouble() method in Java with Examples

The readDouble() method of DataInputStream class in Java is used to read eight input bytes and returns a double value. This method reads the next eight bytes from the input stream and interprets it into double type and returns.

Syntax:

public final double readDouble()
                  throws IOException

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

Parameters: This method does not accept any parameter.

Return value: This method returns the double value interpreted by the next eight bytes of the input stream.

Exceptions:

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

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

Program 1: Assume the existence of file “demo.txt”.

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

        // Create double array
        double[] buf = { 10, 20, 30, 40, 50 };

        // Create file output stream
        FileOutputStream outputStream
            = new FileOutputStream("c:\\demo.txt");

        // Create data output stream
        DataOutputStream dataOutputStr
            = new DataOutputStream(outputStream);

        for (double b : buf) {
            // Write double value to
            // the dataOutputStream
            dataOutputStr.writeDouble(b);
        }

        dataOutputStr.flush();

        // Create file input stream
        FileInputStream inputStream
            = new FileInputStream("c:\\demo.txt");

        // Create data input stream
        DataInputStream dataInputStr
            = new DataInputStream(inputStream);

        while (dataInputStr.available() > 0) {
            // Print double values
            System.out.println(
                dataInputStr.readDouble());
        }
    }
}

Output:

Program 2: Assume the existence of file “demo.txt”.

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

        // Create double array
        double[] buf = { 10.9, 20.8,
                         30.88, 40.76,
                         50.678 };

        // Create file output stream
        FileOutputStream outputStream
            = new FileOutputStream("c:\\demo.txt");

        // Create data output stream
        DataOutputStream dataOutputStr
            = new DataOutputStream(outputStream);

        for (double b : buf) {
            // Write double value to
            // the dataOutputStream
            dataOutputStr.writeDouble(b);
        }

        dataOutputStr.flush();

        // Create file input stream
        FileInputStream inputStream
            = new FileInputStream("c:\\demo.txt");

        // Create data input stream
        DataInputStream dataInputStr
            = new DataInputStream(inputStream);

        while (dataInputStr.available() > 0) {
            // Print double values
            System.out.println(
                dataInputStr.readDouble());
        }
    }
}

Output:

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