Home » Java programming language

Java OutputStream flush() Method with Example

OutputStream Class flush() method: Here, we are going to learn about the flush() method of OutputStream Class with its syntax and example.
Submitted by Preeti Jain, on April 16, 2020

OutputStream Class flush() method

• flush() method is available in java.io package.
• flush() method is used to flush this OuputStream and force output bytes to be written out of any buffer. Let suppose when already any bytes written have been buffered by the implementation of OutputStream, those bytes should be written to the relevant destination immediately.
• 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 performing.

Syntax:

    public void flush();

Parameter(s):

• It does not accept any parameter.

Return value:

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

Example:

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

import java.io.*;

public class FlushOfOS {
 public static void main(String[] args) throws Exception {
  OutputStream os_stm = null;
  InputStream is_stm = null;
  int val = 65;
  
  try {
   // Instantiates FileOutputStream and 
   // FileInputStream 
   os_stm = new FileOutputStream("D:\\includehelp.txt");
   is_stm = new FileInputStream("D:\\includehelp.txt");

   // Loop to write byte to the stream
   for (int i = 0; i < 3; ++i) {
    os_stm.write(val);
    val++;
   }

   // By using flush() method is to
   // flush the stream
   os_stm.flush();

   // Loop to read byte from the stream
   for (int i = 0; i < 3; ++i) {
    char ch = (char) is_stm.read();
    System.out.println("ch: " + ch);
   }
  } catch (Exception ex) {
   System.out.println("Stream Closed Before...");
  } finally {
   // with the help of this block is to
   // free all necessary resources linked
   // with the stream
   if (is_stm != null) {
    is_stm.close();
    if (os_stm != null) {
     os_stm.close();
    }
   }
  }
 }
}

Output

ch: A
ch: B
ch: C