Java - ObjectOutputStream writeInt(int val) method

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Description

The Java ObjectOutputStream writeInt(int val) method writes a 32 bit int.

• It writes the 4-byte (32-bit) binary representation of the int value to the output stream.

• This is not object serialization - it's raw binary writing.

• Paired with readInt() for deserialization.

Declaration

Following is the declaration for java.io.ObjectOutputStream.writeInt(int val) method.

public void writeInt(int val)

Parameters

• val − The int value to be written.

Return Value

This method does not return a value.

Exception

• IOException − If I/O errors occur while writing to the underlying stream.

Example - Usage of ObjectOutputStream writeInt(int val) method

The following example shows the usage of ObjectOutputStream writeInt(int val) method.

ObjectOutputStreamDemo.java

package com.tutorialspoint;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class ObjectOutputStreamDemo {
   public static void main(String[] args) {
      int i = 18764;
      
      try {
         // create a new file with an ObjectOutputStream
         FileOutputStream out = new FileOutputStream("test.txt");
         ObjectOutputStream oout = new ObjectOutputStream(out);

         // write something in the file
         oout.writeInt(i);
         oout.writeInt(497635);

         // close the stream
         oout.close();

         // create an ObjectInputStream for the file we created before
         ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.txt"));

         // read and print what we wrote before
         System.out.println("" + ois.readInt());
         System.out.println("" + ois.readInt());
      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }
}

Output

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

18764
497635

Example - Write and read a single integer

The following example shows the usage of ObjectOutputStream writeInt(int val) method. We're writing the integer 2025 using writeInt() and reading it back.

ObjectOutputStreamDemo.java

package com.tutorialspoint;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class ObjectOutputStreamDemo {
   public static void main(String[] args) {
      String filename = "int1.bin";

      // Write an int
      try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(filename))) {
         oos.writeInt(2025);
         System.out.println("Wrote int: 2025");
      } catch (IOException e) {
         e.printStackTrace();
      }

      // Read the int
      try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(filename))) {
         int value = ois.readInt();
         System.out.println("Read int: " + value);
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output

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

Wrote int: 2025
Read int: 2025

Example - Write a list of integers (e.g. IDs) and read them back

The following example shows the usage of ObjectOutputStream writeInt(int val) method. We're writing several integers representing user IDs.

ObjectOutputStreamDemo.java

package com.tutorialspoint;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class ObjectOutputStreamDemo {
   public static void main(String[] args) {
      String filename = "int_ids.bin";
      int[] userIds = {1001, 1002, 1003, 1004};

      // Write all integers
      try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(filename))) {
         for (int id : userIds) {
            oos.writeInt(id);
         }
         System.out.println("Wrote user IDs.");
      } catch (IOException e) {
         e.printStackTrace();
      }

      // Read them back
      try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(filename))) {
         System.out.println("Reading user IDs:");
         for (int i = 0; i < userIds.length; i++) {
            int id = ois.readInt();
            System.out.println(" - " + id);
         }
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output

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

Wrote user IDs.
Reading user IDs:
 - 1001
 - 1002
 - 1003
 - 1004