byte [] byteArray = new byte[10];             //creates a byte array where the data read should be stored
if(fis.read(byteArray)>0){                    //reads the data into the byte array and returns the number of bytes read
    for(int i=0;i

Writing Into a File Using FileOutputStream




You need to write a Java program to write the answers of a candidate into a file named Answers.txt. Here, your program becomes the source to itself and Answers.txt file becomes the destination.

Look into the below sample code to write your data into Answers.txt file.
public class FileOutputStreamTester{
    public static void main(String[] args)  {
        OutputStream fos=null;
        try{
            fos = new FileOutputStream("Answers.txt");  //1. creates an instance of OutputStream pointing the file in the given path
            fos.write(65);                         
            fos.write(67);                              //2. writes one byte of data into file
            System.out.println("Data written successfully");
        } catch (IOException ioe) {
            System.err.println("Error :"+ioe.getMessage());
        } finally {
            try{
                if(fos!=null){
                       fos.close();                      //3. closes the FileOutputStream
                }
            } catch (IOException ioe) { 
                System.err.println("Error :"+ioe.getMessage()); 
            }
        }
    }
}
   

Below are the steps we used in the code.


Create an instance of OutputStream


Write data byte by byte


Close the stream (As discussed while reading)



Let us discuss about first two steps in detail.  The third step, close the stream, is same as closing the stream in FileInputStream. The close() method of that specific stream has to be invoked.

Creating an Instance of OutputStream

Java Program needs an instance of OutputStream for writing byte data into a file.  For example, if your program needs to perform a write operation on a file named ‘Answers.txt', it requires an OutputStream object. Based on whether you want to overwrite or append into the given file, you can use either of the below constructors for object creation



The String property filePath represents the absolute or relative path of the file.

Note:  Both the constructors can create a new file if the file is not available in the given path.
String company="Infosys";
byte [] byteArray = company.getBytes();       //converts String to byte array
fos.write(byteArray);                         //writes array of bytes into file



try-with-resources helps us to reduce the code size.  It is an automatic resource management feature added in Java 7 which can close the resources automatically.
 public class FileOutputStreamTester{
2   public static void main(String[] args){
3     try(OutputStream fos = new FileOutputStream("Answers.txt"))
4     {
5         fos.write(65);
6         System.out.println("Data written successfully");
7     }catch (IOException ioe) {
8         System.err.println("Error :"+ioe.getMessage());
9     }
10   }
11 }

Only the AutoCloseable objects, an object that implements java.lang.AutoCloseable interface, can be declared in try-with-resources. The AutoCloseable interface, which is introduced from Java 7, defines a single close() method. If an AutoCloseable object is declared in try block opening (resource specification header), the close() method of that object is called automatically when exiting a try-with-resources block.
try (FileInputstream inputStream = new FileInputstream("file1.txt");
     FileOutputStream outputStream = new FileOutputStream("file2.txt")) { 
  // try block code 
} 
class src2dest 
{ 
    public static void main(String args[]) 
    throws FileNotFoundException,IOException 
    { 
        /* If file doesnot exist FileInputStream throws 
           FileNotFoundException and read() write() throws 
           IOException if I/O error occurs */
        FileInputStream fis = new FileInputStream(args[0]); 
  
        /* assuming that the file exists and need not to be 
           checked */
        FileOutputStream fos = new FileOutputStream(args[1]); 
  
        int b; 
        while  ((b=fis.read()) != -1) 
            fos.write(b); 
  
        /* read() will readonly next int so we used while 
           loop here in order to read upto end of file and 
           keep writing the read int into dest file */
        fis.close(); 
        fos.close(); 
    } 
}