Approaches to write files in Java

This article describes some of the common approaches to write files in Java.

Using OutputStreamWriter with a BufferedReader

Refer the example function below. FileOutputStream is the byte stream here capable of writing raw bytes to the file. OutputStreamWriter is a bridge which converts characters into raw bytes using the specified charset. The OutputStreamWriter is a unbuffered stream. To make the program efficient for writing characters, lines etc. it needs to be wrapped with a buffered stream like the BufferedWriter.

public static void writeStringToFile1(String str) { 
  BufferedWriter writer = null;
  try {
    File file = new File("output/test1.txt");
    if ( ! file.exists() )
      file.createNewFile();

    FileOutputStream fos = new FileOutputStream(file);
    OutputStreamWriter out = new OutputStreamWriter(fos, StandardCharsets.UTF_8);
    writer = new BufferedWriter(out);
    writer.write(str);
    writer.flush();

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

Using FileWriter with a BufferedWriter

Refer the example function below. FileWriter is a convenience class for writing character files. FileWriter assumes the default character encoding. FileWriter is unbuffered and we need to wrap it in a buffered stream to make the program more efficient for reading.

public static void writeToFile2(String str) { 
  BufferedWriter out = null;
  try {
    File file = new File("output/test2.txt");
    if ( ! file.exists() )
      file.createNewFile();

    FileWriter writer = new FileWriter(file);
    out = new BufferedWriter(writer);
    out.write(str);
    out.flush(); 
  } catch ( IOException e ){
    e.printStackTrace();
  }
  finally {
    if ( out != null ) {
      try {
        out.close();
      } catch ( IOException e ){
        e.printStackTrace();
      }
    }
  }
}

Using PrintWriter with a BufferedWriter

Refer the example function below. PrintWriter has the capability to print formatted representations of objects to a text output stream.

public static void writeToFile3(String str) { 
  PrintWriter out = null;
  try {
    File file = new File("output/test3.txt");
    if ( ! file.exists() )
      file.createNewFile();

    BufferedWriter writer = new BufferedWriter(new FileWriter(file));
    out = new PrintWriter(writer);
    out.println(str);
    // Write formatted output
    out.println(true);
    out.println(123.00);
    out.printf("%5d\n", 100);
    out.flush();

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

Using Files for Java7

Java7 has introduced the new file I/O package which provides the Files API to make writing files much simpler. Refer example below.

public static void writeUsingJava7(String str) {
  try {
    Files.write(Paths.get("output/test10.txt"), 
        str.getBytes(), 
        StandardOpenOption.CREATE);
  } catch (IOException e) {
    e.printStackTrace();
  }
}