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Java ObjectOutputStream flush() Method with Example

ObjectOutputStream Class flush() method: Here, we are going to learn about the flush() method of ObjectOutputStream Class with its syntax and example.
Submitted by Preeti Jain, on April 08, 2020

ObjectOutputStream Class flush() method

• flush() method is available in java.io package.
• flush() method is used to flush this stream and write bytes immediately of any buffered output to the underlying stream.
• flush() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• flush() method may throw an exception at the time of flushing the stream.
  IOException: This exception may throw when getting any input/output error while writing to the output stream.

Syntax:

    public void flush();

Parameter(s):

• It does not accept any parameter.

Return value:

The return type of this method is void, it returns nothing.

Example:

// Java program to demonstrate the example 
// of void flush() method of ObjectOutputStream

import java.io.*;

public class FlushOfOOS {
 public static void main(String[] args) throws Exception {
  // Instantiates ObjectOutputStream , ObjectInputStream 
  // FileInputStream and FileOutputStream
  FileOutputStream file_out_stm = new FileOutputStream("D:\\includehelp.txt");
  ObjectOutputStream obj_out_stm = new ObjectOutputStream(file_out_stm);
  FileInputStream file_in_stm = new FileInputStream("D:\\includehelp.txt");
  ObjectInputStream obj_in_stm = new ObjectInputStream(file_in_stm);

  // By using writeByte() method is to
  // write byte to the stream		
  obj_out_stm.writeByte(65);

  // By using flush() method is to
  // flush the stream immediately
  System.out.println("Stream Flushed...");
  obj_out_stm.flush();

  // By using readByte() method is to 
  // read the byte and convert it into
  // char
  char ch = (char) obj_in_stm.read();
  System.out.println("ch: " + ch + " ");

  // By using close() method is to 
  // close all the streams 
  System.out.println("Stream Shutdown... ");

  file_in_stm.close();
  file_out_stm.close();
  obj_in_stm.close();
  obj_out_stm.close();
 }
}

Output

Stream Flushed...
ch: A 
Stream Shutdown...