Java Tutorial/File/FileOutputStream

Append output to file using FileOutputStream

   <source lang="java">

import java.io.FileOutputStream; public class Main {

 public static void main(String[] args) throws Exception {
   FileOutputStream fos = new FileOutputStream("C:/demo.txt", true);
   fos.write("Appended".getBytes());
   fos.close();
 }

}</source>

Copy a file with FileInputStream and FileOutputStream

   <source lang="java">

import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; class CopyFile {

 public static void main(String args[]) throws IOException {
   int i;
   FileInputStream fin;
   FileOutputStream fout;
   fin = new FileInputStream(args[0]);
   fout = new FileOutputStream(args[1]);
   do {
     i = fin.read();
     if (i != -1)
       fout.write(i);
   } while (i != -1);
   fin.close();
   fout.close();
 }

}</source>

Create a file output stream directly from the file name

   <source lang="java">

import java.io.FileNotFoundException; import java.io.FileOutputStream; public class MainClass {

 public static void main(String[] a) {
   FileOutputStream outputFile = null; // Place to store the stream reference
   try {
     outputFile = new FileOutputStream("myFile.txt");
   } catch (FileNotFoundException e) {
     e.printStackTrace(System.err);
   }
 }

}</source>

Create DataOutputStream from FileOutputStream

   <source lang="java">

import java.io.DataOutputStream; import java.io.FileOutputStream; public class Main {

 public static void main(String[] args) throws Exception {
   FileOutputStream fos = new FileOutputStream("C:/demo.txt");
   DataOutputStream dos = new DataOutputStream(fos);
 }

}</source>

Create FileOutputStream object from File object

   <source lang="java">

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

 public static void main(String[] args) throws Exception {
   File file = new File("C:/demo.txt");
   FileOutputStream fos = new FileOutputStream(file);
 }

}</source>

Create FileOutputStream object from String file path

   <source lang="java">

import java.io.FileOutputStream; public class Main {

 public static void main(String[] args) throws Exception {
   FileOutputStream fos = new FileOutputStream("C:/demo.txt");
 }

}</source>

File IO

   <source lang="java">

import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; public class FileIOApp {

 public static void main(String args[]) throws IOException {
   FileOutputStream outStream = new FileOutputStream("test.txt");
   String s = "This is a test.";
   for (int i = 0; i < s.length(); ++i)
     outStream.write(s.charAt(i));
   outStream.close();
   FileInputStream inStream = new FileInputStream("test.txt");
   int inBytes = inStream.available();
   System.out.println("inStream has " + inBytes + " available bytes");
   byte inBuf[] = new byte[inBytes];
   int bytesRead = inStream.read(inBuf, 0, inBytes);
   System.out.println(bytesRead + " bytes were read");
   System.out.println("They are: " + new String(inBuf));
   inStream.close();
   File f = new File("test.txt");
   f.delete();
 }

}</source>

FileOutputStream

1. The FileOutputStream class is a subclass of OutputStream.
2. You can construct a FileOutputStream object by passing a string containing a path name or a File object.
3. You can also specify whether you want to append the output to an existing file.

   <source lang="java">

public FileOutputStream (String path) public FileOutputStream (String path, boolean append) public FileOutputStream (File file) public FileOutputStream (File file, boolean append)</source>

Forcing Updates to a File to the Disk

   <source lang="java">

import java.io.FileDescriptor; import java.io.FileOutputStream; public class Main {

 public static void main(String[] argv) throws Exception {
   FileOutputStream os = new FileOutputStream("outfilename");
   FileDescriptor fd = os.getFD();
   os.write(1);
   os.flush();
   fd.sync();
 }

}</source>

Get FileChannel from FileOutputStream

   <source lang="java">

// Getting channels from streams import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.RandomAccessFile; import java.nio.ByteBuffer; import java.nio.channels.FileChannel; public class MainClass {

 private static final int BSIZE = 1024;
 public static void main(String[] args) throws Exception {
   FileChannel fc = new FileOutputStream("data.txt").getChannel();
   fc.write(ByteBuffer.wrap("Some text ".getBytes()));
   fc.close();
 }

}</source>

serializes an object to an output stream.

   <source lang="java">

/*

* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
* 
*      http://www.apache.org/licenses/LICENSE-2.0
* 
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

import java.io.BufferedOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectOutputStream;

public class Main {

 /**
  * This method serializes an object to an output stream.
  *
  * @param file The output file
  * @param object The object to be serialized
  * @exception IOException IOError
  */
 public static void serializeObject(File file, Object object)
 throws IOException {
     FileOutputStream fos = new FileOutputStream(file);
     try {
         ObjectOutputStream oos = new ObjectOutputStream(new BufferedOutputStream(fos));
         oos.writeObject(object);
         oos.flush();
     } finally {
         fos.close();
     }
 }

}</source>

Use FileOutputStream to read integers

   <source lang="java">

import java.io.ByteArrayOutputStream; import java.io.DataOutputStream; import java.io.FileOutputStream; import java.io.IOException; public class MainClass {

 public static void main(String args[]) throws IOException {
   int howMany = 20;
   // To avoid resizing the buffer, calculate the size of the
   // byte array in advance.
   ByteArrayOutputStream bout = new ByteArrayOutputStream(howMany * 4);
   DataOutputStream dout = new DataOutputStream(bout);
   for (int i = 0; i <= 20; i++) {
     dout.writeInt(i);
   }
   FileOutputStream fout = new FileOutputStream("fibonacci.dat");
   try {
     bout.writeTo(fout);
     fout.flush();
   } finally {
     fout.close();
   }
 }

}</source>

Use FileOutputStream to write the bytes to a file.

   <source lang="java">

import java.io.FileOutputStream; public class Main {

 public static void main(String[] argv) throws Exception {
   byte[] vals = { 65, 66, 67, 68, 69, 70, 71, 72, 73, 74 };
   FileOutputStream fout = new FileOutputStream("Test.dat");
   for (int i = 0; i < vals.length; i += 2)
     fout.write(vals[i]);
   fout.close();
 }

}</source>

Write byte array to a file using FileOutputStream

   <source lang="java">

import java.io.FileOutputStream; public class Main {

 public static void main(String[] args) throws Exception {
   String strFilePath = "C://demo.txt";
   FileOutputStream fos = new FileOutputStream(strFilePath);
   String strContent = "Write File using Java FileOutputStream example !";
   fos.write(strContent.getBytes());
   fos.close();
 }

}</source>

Write double to a file using DataOutputStream

   <source lang="java">

import java.io.DataOutputStream; import java.io.FileOutputStream; public class Main {

 public static void main(String[] args) throws Exception {
   String strFilePath = "C:/Double.txt";
   FileOutputStream fos = new FileOutputStream(strFilePath);
   DataOutputStream dos = new DataOutputStream(fos);
   double d = 1;
   dos.writeDouble(d);
   dos.close();
 }

}</source>

Write file using FileOutputStream

   <source lang="java">

import java.io.FileOutputStream; public class Main {

 public static void main(String[] args) throws Exception {
   FileOutputStream fos = new FileOutputStream("C:/demo.txt");
   byte b = 01;
   fos.write(b);
   fos.close();
 }

}</source>

Write UTF String, integer and double with DataOutputStream

   <source lang="java">

import java.io.BufferedOutputStream; import java.io.DataOutputStream; import java.io.FileOutputStream; public class Main {

 public static void main(String[] argv) throws Exception {
   FileOutputStream fileOut = new FileOutputStream("data.txt");
   BufferedOutputStream buffer = new BufferedOutputStream(fileOut);
   DataOutputStream dataOut = new DataOutputStream(buffer);
   dataOut.writeUTF("Hello!");
   dataOut.writeInt(4);
   dataOut.writeDouble(100.0);
   dataOut.close();
   buffer.close();
   fileOut.close();
 }

}</source>