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- Java.io - ObjectInputStream
- Java.io - ObjectInputStream.GetField
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- io - ObjectOutputStream.PutField
- Java.io - ObjectStreamClass
- Java.io - ObjectStreamField
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- Java.io package extras
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- Java.io package Useful Resources
- Java.io - Discussion
Java.io.ObjectOutputStream.writeUnshared() Method
Description
The java.io.ObjectOutputStream.writeUnshared(Object obj) method writes an "unshared" object to the ObjectOutputStream. This method is identical to writeObject, except that it always writes the given object as a new, unique object in the stream (as opposed to a back-reference pointing to a previously serialized instance).Specifically −
An object written via writeUnshared is always serialized in the same manner as a newly appearing object (an object that has not been written to the stream yet), regardless of whether or not the object has been written previously.
If writeObject is used to write an object that has been previously written with writeUnshared, the previous writeUnshared operation is treated as if it were a write of a separate object. In other words, ObjectOutputStream will never generate back-references to object data written by calls to writeUnshared.
While writing an object via writeUnshared does not in itself guarantee a unique reference to the object when it is deserialized, it allows a single object to be defined multiple times in a stream, so that multiple calls to readUnshared by the receiver will not conflict. Note that the rules described above only apply to the base-level object written with writeUnshared, and not to any transitively referenced sub-objects in the object graph to be serialized.
ObjectOutputStream subclasses which override this method can only be constructed in security contexts possessing the "enableSubclassImplementation" SerializablePermission; any attempt to instantiate such a subclass without this permission will cause a SecurityException to be thrown.
Declaration
Following is the declaration for java.io.ObjectOutputStream.writeUnshared() method.
public void writeUnshared(Object obj)
Parameters
obj − object to write to stream.
Return Value
This method does not return a value.
Exception
NotSerializableException − If an object in the graph to be serialized does not implement the Serializable interface.
InvalidClassException − If a problem exists with the class of an object to be serialized.
IOException − If an I/O error occurs during serialization.
Example
The following example shows the usage of java.io.ObjectOutputStream.writeUnshared() method.
package com.tutorialspoint; import java.io.*; public class ObjectOutputStreamDemo { public static void main(String[] args) { Object s = "Hello World!"; Object i = 1974; try { // create a new file with an ObjectOutputStream FileOutputStream out = new FileOutputStream("test.txt"); ObjectOutputStream oout = new ObjectOutputStream(out); // write something in the file oout.writeUnshared(s); oout.writeUnshared(i); // close the stream oout.close(); // create an ObjectInputStream for the file we created before ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.txt")); // read and print what we wrote before System.out.println("" + ois.readUnshared()); System.out.println("" + ois.readUnshared()); } catch (Exception ex) { ex.printStackTrace(); } } }
Let us compile and run the above program, this will produce the following result −
Hello World! 1974