Wrap FileWriter with BufferedWriter : FileWriter « File « Java Tutorial

1. Java Tutorial
2. File
3. FileWriter

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;

public class AllCapsDemo {
  public static void main(String[] arguments) {
    String sourceName = "asdf";
    try {
      File source = new File(sourceName);
      File temp = new File("cap" + sourceName + ".tmp");

      FileReader fr = new FileReader(source);
      BufferedReader in = new BufferedReader(fr);

      FileWriter fw = new FileWriter(temp);
      BufferedWriter out = new BufferedWriter(fw);

      boolean eof = false;
      int inChar = 0;
      do {
        inChar = in.read();
        if (inChar != -1) {
          char outChar = Character.toUpperCase((char) inChar);
          out.write(outChar);
        } else
          eof = true;
      } while (!eof);
      in.close();
      out.close();

      boolean deleted = source.delete();
      if (deleted)
        temp.renameTo(source);
    } catch (Exception se) {
      System.out.println("Error - " + se.toString());
    }
  }
}