Java Tutorial/File/FileWriter

Append or add some contents to the file

   <source lang="java">

import java.io.File; import java.io.FileWriter; public class Main {

 public static void main(String[] args) throws Exception{
   File file = new File("user.txt");
   FileWriter writer = new FileWriter(file, true);
   writer.write("username=java;password=secret" + System.getProperty("line.separator"));
   writer.flush();
   writer.close();
 }

}</source>

FileWriter

1. FileWriter provides a convenient way of writing characters to a file.
2. FileWriter uses your computer"s default character encoding.

   <source lang="java">

public FileWriter (File file) public FileWriter (File file, boolean append) public FileWriter (String path) public FileWriter (String path, boolean append) public FileWriter (FileDescriptor fileDescriptor)</source>

Use FileWriter to write an array of strings to a file.

   <source lang="java">

import java.io.FileWriter; public class Main {

 public static void main(String[] argv) throws Exception {
   FileWriter fw = new FileWriter("file.dat");
   String strs[] = { "com", "exe", "doc" };
   for (int i = 0; i < strs.length; i++) {
     fw.write(strs[i] + "\n");
   }
   fw.close();
 }

}</source>

Wrap FileWriter with BufferedWriter

   <source lang="java">

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());
   }
 }

}</source>