Java Tutorial/File/ObjectOutputStream

Create a serialized output file.

   <source lang="java">

import java.io.FileOutputStream; import java.io.ObjectOutput; import java.io.ObjectOutputStream; import java.io.Serializable; public class MainClass {

 // Throw exceptions to console:
 public static void main(String[] args) throws Exception {
   ObjectOutput out = new ObjectOutputStream(new FileOutputStream("X.file"));
   MyClass zorcon = new MyClass();
   out.writeObject(zorcon);
 }

} // A serializable class. class MyClass implements Serializable { }</source>

Create ObjectOutputStream out of FileOutputStream

   <source lang="java">

import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectOutputStream; import java.io.Serializable; import java.util.Date; public class ObjectWriter {

 public static void main(String[] arguments) {
   Message mess = new Message();
   String author = "London";
   String recipient = "G, B";
   String[] letter = { "Merry Christmas." };
   Date now = new Date();
   mess.writeMessage(author, recipient, now, letter);
   try {
     FileOutputStream fo = new FileOutputStream("Message.obj");
     ObjectOutputStream oo = new ObjectOutputStream(fo);
     oo.writeObject(mess);
     oo.close();
     System.out.println("Object created successfully.");
   } catch (IOException e) {
     System.out.println("Error - " + e.toString());
   }
 }

} class Message implements Serializable {

 int lineCount;
 String from, to;
 Date when;
 String[] text;
 void writeMessage(String inFrom, String inTo, Date inWhen, String[] inText) {
   text = new String[inText.length];
   for (int i = 0; i < inText.length; i++)
     text[i] = inText[i];
   lineCount = inText.length;
   to = inTo;
   from = inFrom;
   when = inWhen;
 }

}</source>

illustrates serialization and deserialization

   <source lang="java">

import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; class shutdown {

 public static void main(String[] args) throws ClassNotFoundException, IOException {
   FileOutputStream fos = new FileOutputStream("objects.tmp");
   ObjectOutputStream oos = new ObjectOutputStream(fos);
   oos.writeObject("asdf");
   oos.flush();
   fos.close();
   
   FileInputStream fis = new FileInputStream ("objects.tmp");  
   ObjectInputStream ois = new ObjectInputStream (fis);  
   String t = (String) ois.readObject ();  
   fis.close ();   
   
 }

}</source>

Object IO

   <source lang="java">

import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.Serializable; import java.util.Date; public class ObjectIOApp {

 public static void main(String args[]) throws IOException, ClassNotFoundException {
   File file = new File("test.txt");
   FileOutputStream outFile = new FileOutputStream(file);
   ObjectOutputStream outStream = new ObjectOutputStream(outFile);
   TestClass1 t1 = new TestClass1(true, 9, "A", 0.0001, "java");
   TestClass2 t2 = new TestClass2();
   String t3 = "This is a test.";
   Date t4 = new Date();
   outStream.writeObject(t1);
   outStream.writeObject(t2);
   outStream.writeObject(t3);
   outStream.writeObject(t4);
   outStream.close();
   outFile.close();
   FileInputStream inFile = new FileInputStream(file);
   ObjectInputStream inStream = new ObjectInputStream(inFile);
   System.out.println(inStream.readObject());
   System.out.println(inStream.readObject());
   System.out.println(inStream.readObject());
   System.out.println(inStream.readObject());
   inStream.close();
   inFile.close();
   file.delete();
 }

} class TestClass1 implements Serializable {

 boolean b;
 int i;
 char c;
 double d;
 String s;
 TestClass1(boolean b, int i, char c, double d, String s) {
   this.b = b;
   this.i = i;
   this.c = c;
   this.d = d;
   this.s = s;
 }
 public String toString() {
   String r = String.valueOf(b) + " ";
   r += String.valueOf(i) + " ";
   r += String.valueOf(c) + " ";
   r += String.valueOf(d) + " ";
   r += String.valueOf(s);
   return r;
 }

} class TestClass2 implements Serializable {

 int i;
 TestClass1 tc1;
 TestClass1 tc2;
 TestClass2() {
   i = 0;
   tc1 = new TestClass1(true, 2, "j", 1.234, "Java");
   tc2 = new TestClass1(false, 7, "J", 2.468, "JAVA");
 }
 public String toString() {
   String r = String.valueOf(i) + " ";
   r += tc1.toString() + " ";
   r += tc2.toString();
   return r;
 }

}</source>

Reading Basic Data From an Object Stream

   <source lang="java">

import java.awt.Polygon; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; public class MainClass {

 public static void main(String[] args) {
   int[] x = new int[] { 1, 2, 3 };
   int[] y = new int[] { 4, 5, 6 };
   Polygon polygon = new Polygon(x, y, x.length);
   try {
     ObjectOutputStream objectOut = new ObjectOutputStream(new BufferedOutputStream(
         new FileOutputStream("C:/Polygons.bin")));
     objectOut.writeObject(polygon);
     objectOut.close();
   } catch (IOException e) {
     e.printStackTrace(System.err);
   }
   try {
     ObjectInputStream objectIn = new ObjectInputStream(new BufferedInputStream(
         new FileInputStream("C:/Polygons.bin")));
     Polygon theLine = (Polygon) objectIn.readObject();
     System.out.println(theLine);
     objectIn.close();
   } catch (Exception e) {
     e.printStackTrace(System.err);
   }
 }

}</source>

Serializing an Object (JButton)

   <source lang="java">

import java.io.ByteArrayOutputStream; import java.io.FileOutputStream; import java.io.ObjectOutput; import java.io.ObjectOutputStream; import javax.swing.JButton; public class Main {

 public static void main(String[] argv) throws Exception {
   Object object = new JButton("push me");
   ObjectOutput out = new ObjectOutputStream(new FileOutputStream("filename.ser"));
   out.writeObject(object);
   out.close();
   // Serialize to a byte array
   ByteArrayOutputStream bos = new ByteArrayOutputStream();
   out = new ObjectOutputStream(bos);
   out.writeObject(object);
   out.close();
   // Get the bytes of the serialized object
   byte[] buf = bos.toByteArray();
   System.out.println(new String(buf));
 }

}</source>

Try to recover a serialized file without the class of object that"s stored in that file

   <source lang="java">

import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.ObjectInputStream; import java.io.ObjectOutput; import java.io.ObjectOutputStream; import java.io.Serializable; public class MainClass {

 public static void main(String[] args) throws Exception {
   ObjectOutput out = new ObjectOutputStream(new FileOutputStream("X.file"));
   MyClass zorcon = new MyClass();
   out.writeObject(zorcon);
   
   ObjectInputStream in = new ObjectInputStream(new FileInputStream(new File("X.file")));
     Object mystery = in.readObject();
     System.out.println(mystery.getClass());
   
 }

} // A serializable class. class MyClass implements Serializable { }</source>

Writing objects to file with ObjectOutputStream

   <source lang="java">

import java.io.FileOutputStream; import java.io.ObjectOutputStream; import java.io.Serializable; class Person implements Serializable {

 private String firstName;
 private String lastName;
 private int age;
 public Person() {
 }
 public String getFirstName() {
   return firstName;
 }
 public void setFirstName(String firstName) {
   this.firstName = firstName;
 }
 public String getLastName() {
   return lastName;
 }
 public void setLastName(String lastName) {
   this.lastName = lastName;
 }
 public int getAge() {
   return age;
 }
 public void setAge(int age) {
   this.age = age;
 }
 public String toString() {
   StringBuffer buffer = new StringBuffer();
   buffer.append(firstName);
   buffer.append("\n");
   buffer.append(lastName);
   buffer.append("\n");
   buffer.append(age);
   buffer.append("\n");
   return buffer.toString();
 }

} public class Main {

 public static void main(String[] args) throws Exception {
   ObjectOutputStream outputStream = null;
   outputStream = new ObjectOutputStream(new FileOutputStream("yourFile.dat"));
   Person person = new Person();
   person.setFirstName("A");
   person.setLastName("B");
   person.setAge(38);
   outputStream.writeObject(person);
   person = new Person();
   person.setFirstName("C");
   person.setLastName("D");
   person.setAge(22);
   outputStream.writeObject(person);
 }

}</source>