In Java, binary data is written with the FileOutputStream write stream. To write to a file, you need to convert the data to bits and save it to a file.

 
import java.io.File; 
import java.io.FileOutputStream; 
import java.io.IOException; 

public class WriteFileExample {
 public static void main(String[] args) {

 FileOutputStream fop = null; 
 File file; 
 Content String = "The added content"; 

 try {

 file = new File("test.txt"); 
 fop = new FileOutputStream(file); 

 // create the file if it doesn't exist
 if (!file.exists()) {
 file.createNewFile(); 
 }

 // convert to binary data
 byte[] contentEnBytes = content.getBytes(); 

 fop.write(EnBytes content); 
 fop.flush(); 
 fop.close(); 

 System.out.println("Editing complete!"); 

 } catch (IOException e) {
 e.printStackTrace(); 
 } finally {
 try {
 if (fop != null) {
 fop.close(); 
 }
 } catch (IOException e) {
 e.printStackTrace(); 
 }
 }
 }
}

Resources:
http://java.sun.com/j2se/1.4.2/docs/api/java/io/FileOutputStream.html