How to Write to a file with JAVA

The task of writing to a file with Java is greatly simplified with Input/Output streams. These are a group of classes used for basic I/O and include classes for serialization that allows a program to read and write entire objects to a stream. Many methods of writing to a file can be employed and they are included in the java.io package. Here's a simple example of writing to a file with Java.

Instructions

1. Import all of the needed classes. We import each class individually for the purposes of illustration but we could import the entire package with the statement "import java.io.*."

2. Declare a FileInputStream object for the input and output files and instantiate them with the desired input and output file names (input.txt and output.txt, respectively).

3. Use the write method of the FileOutputStream class to write to the output file. Other methods are available for writing to a file, but write is used here as the simplest possible example.

4. Notice how the program stays in a loop that reads a byte from the input stream and writes the byte to the output stream until the end of the input file is reached.

5. Look at the complete code for this example:

   import java.io.FileInputStream;
   import java.io.FileOutputStream;
   import java.io.IOException;

   public class WriteBytes {
   public static void main(String[] args) throws IOException {
   FileInputStream in = null;
   FileOutputStream out = null;
   try {
   int i;
   in = new FileInputStream("input.txt");
   out = new FileOutputStream("output.txt");

   while ((i = in.read()) != -1){
   out.write(i);
   }
   }
   finally {
   if (in != null) {
   in.close();
   }
   if (out != null) {
   out.close();
   }
   }
   }
   }

Resources

• Learn more about java programs.