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The readInt() method of DataInputStream class in Java is used to read four input bytes and returns a integer value. This method reads the next four bytes from the input stream and interprets it into integer type and returns. Syntax:

public final int readInt()
             throws IOException

Specified By: This method is specified by readInt() method of DataInput interface. Parameters: This method does not accept any parameter. Return value: This method returns the int value interpreted by the next four bytes of the input stream. Exceptions:

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

Below programs illustrate readInt() method in DataInputStream class in IO package: Program 1: Assume the existence of file "demo.txt".

Java

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

        // Create integer array
        int[] 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 (int b : buf) {
            // Write integer value to
            // the dataOutputStream
            dataOutputStr.writeInt(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 integer values
            System.out.println(
                dataInputStr.readInt());
        }
    }
}

Output:

Program 2: Assume the existence of file "demo.txt".

Java

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

        // Create integer array
        int[] buf = { 191, 225, 480, 763, 500 };

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

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

        for (int b : buf) {
            // Write integer value to
            // the dataOutputStream
            dataOutputStr.writeInt(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 integer values
            System.out.println(
                dataInputStr.readInt());
        }
    }
}

Output:

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

DataInputStream readInt() method in Java with Examples

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