DataInputStream readInt() method in Java with Examples

Last Updated : 05 Jun, 2020

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 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 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()); 
        } 
    } 
} 