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