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Java DataOutputStream flush() Method with Example

DataOutputStream Class flush() method: Here, we are going to learn about the flush() method of DataOutputStream Class with its syntax and example.
Submitted by Preeti Jain, on March 30, 2020

DataOutputStream Class flush() method

• flush() method is available in java.io package.
• flush() method is used to flush this stream and forces bytes to be written to the basic 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.

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 DataOutputStream

import java.io.*;

public class FlushOfDOS {
 public static void main(String[] args) throws IOException {
  InputStream is_stm = null;
  DataInputStream dis_stm = null;
  FileOutputStream fos_stm = null;
  DataOutputStream dos_stm = null;
  byte[] b_arr = {
   12,
   20,
   45,
   98,
   75,
   69,
   30,
   58,
   47,
   61,
   83,
   55
  };

  try {
   // Instantiate FileInputStream, 
   // DataInputStream, FileOutputStream
   // and DataOutputStream 

   fos_stm = new FileOutputStream("C:\\Users\\Preeti Jain\\Desktop\\programs\\includehelp.txt");
   dos_stm = new DataOutputStream(fos_stm);
   is_stm = new FileInputStream("C:\\Users\\Preeti Jain\\Desktop\\programs\\includehelp.txt");
   dis_stm = new DataInputStream(is_stm);

   // Loop to write each byte till end
   for (byte val: b_arr) {
    // By using write() method isto
    // write a byte value to the
    // DataOutputStream dos_stm
    dos_stm.write(val);
   }

   // By using flush() method isto
   // flush the stream and forces bytes
   // are written out immediately of any 
   // buffered output
   dos_stm.flush();

   // Loop To Read Available Data till end
   while (dis_stm.available() > 0) {
    // By using read() method isto read 
    // byte from dis_stm
    int in = dis_stm.read();
    System.out.println("dis_stm.read(): " + in );
   }
  } catch (Exception ex) {
   System.out.println(ex.toString());
  } finally {
   // To free system resources linked
   // with these streams
   if (is_stm != null)
    is_stm.close();

   if (dis_stm != null)
    dis_stm.close();

   if (dos_stm != null)
    dos_stm.close();

   if (fos_stm != null)
    fos_stm.close();
  }
 }
}

Output

dis_stm.read(): 12
dis_stm.read(): 20
dis_stm.read(): 45
dis_stm.read(): 98
dis_stm.read(): 75
dis_stm.read(): 69
dis_stm.read(): 30
dis_stm.read(): 58
dis_stm.read(): 47
dis_stm.read(): 61
dis_stm.read(): 83
dis_stm.read(): 55