- What is lazy and early loading of Singleton?
- Can we serialize final variable in Java?
- What is true serialization?
- How can we avoid cloning of singleton objects?
- Can we clone singleton object?
- What is ObjectInputStream in Java?
- What is the purpose of readResolve () method in serialization?
- Which methods are used during serialization and deserialization process?
- Where is Singleton pattern used?
- Which interface gives more control on serialization of an object?
- Can we extend singleton class in Java?
- How will you achieve serialization if the object is Singleton?
- How can we prevent Singleton class from serialization?
- How do you break a singleton with reflection?
- What is difference between final and immutable?
- Can immutable class be serializable?
- What is the difference between serialization and Deserialization?
- Is string serializable in Java?
- What is Externalizable?
- How can we prevent immutable class from serialization?
- Why is serialization required?
What is lazy and early loading of Singleton?
Both these refer to when the Singleton object gets created in the application.
In lazy loading it is created only when the method creating the instance is first called.
In early loading the instance is created once the class is loaded..
Can we serialize final variable in Java?
A final variable can only be assigned once. Remove the final modifier, and try again. A requirement of a Java class that is serializable is that it has access to a no-argument constructor in its first non-serializable superclass. Java serialization utilizes this no-arg constructor.
What is true serialization?
Serialization provides a way where an object can be represented as a sequence of bytes which includes the object’s data and information having the object’s type and the types of data stored in the object. It can only be read from the file after the serialized object is written into a file.
How can we avoid cloning of singleton objects?
You can avoid cloning by giving already created object by clone method. You need to override the clone() method only if your singleton class implements Cloneable interface or a class which implements Cloneable interface.
Can we clone singleton object?
clone() is protected method and as every class in java by default extends Object class, object of any class including our Singleton class can call clone() method. If somebody will call instance. … So, if we are not implementing Cloneable interface in our Singleton class, then we do not require to prevent cloning.
What is ObjectInputStream in Java?
The Java ObjectInputStream class ( java. io. ObjectInputStream ) enables you to read Java objects from an InputStream instead of just raw bytes. … Otherwise reading objects will fail. Normally you will use the ObjectInputStream to read objects written (serialized) by a Java ObjectOutputStream .
What is the purpose of readResolve () method in serialization?
For Serializable and Externalizable classes, the readResolve method allows a class to replace/resolve the object read from the stream before it is returned to the caller. By implementing the readResolve method, a class can directly control the types and instances of its own instances being deserialized.
Which methods are used during serialization and deserialization process?
The ObjectOutputStream class contains writeObject() method for serializing an Object. The ObjectInputStream class contains readObject() method for deserializing an object.
Where is Singleton pattern used?
In terms of practical use Singleton patterns are used in logging, caches, thread pools, configuration settings, device driver objects. Design pattern is often used in conjunction with Factory design pattern. This pattern is also used in Service Locator JEE pattern.
Which interface gives more control on serialization of an object?
Externalizable interfaceFor complete, explicit control of the serialization process, a class must implement the Externalizable interface. For Externalizable objects, only the identity of the object’s class is automatically saved by the stream.
Can we extend singleton class in Java?
All you need to extend a singleton class is a constructor with protected or package-default in the singleton class. If there are only private constructors you simply won’t be able to extend it. If there are public constructors then it’s not a singleton class.
How will you achieve serialization if the object is Singleton?
Conclusion: Singleton class can also be serialized by keeping readResolve() method in the Singleton class. This may be a familiar solution but just in case for reference. So if we execute above code we will get following behaviour: “it has created two objects and one static reference for INSTANCE.
How can we prevent Singleton class from serialization?
In serialization, we can save the object of a byte stream into a file or send over a network. Suppose if you serialize the Singleton class, and then again de-serialize that object, it will create a new instance, hence deserialization will break the Singleton pattern.
How do you break a singleton with reflection?
As it is not possible to call enum constructor from the program, it is not possible for us to access them by Reflection also. Hence, reflection can’t break singleton property in case of enums. Enum Singleton cannot be broken using Serialization and Enums are also by default thread-safe.
What is difference between final and immutable?
final means that you can’t change the object’s reference to point to another reference or another object, but you can still mutate its state (using setter methods e.g). Whereas immutable means that the object’s actual value can’t be changed, but you can change its reference to another one.
Can immutable class be serializable?
It turns out you can serialize immutable objects because there’s no requirement that there be a public no-argument constructor.
What is the difference between serialization and Deserialization?
Serialization takes an in-memory data structure and converts it into a series of bytes that can be stored and transferred. Deserialization takes a series of bytes and converts it to an in-memory data structure that can be consumed programmatically.
Is string serializable in Java?
The String class and all the wrapper classes implement the java. io. Serializable interface by default.
What is Externalizable?
Externalizable is an interface that enables you to define custom rules and your own mechanism for serialization. … Externalizable extends Serializable. Implement writeExternal and readExternal methods of the Externalizable interface and create your own contract / protocol for serialization.
How can we prevent immutable class from serialization?
If an immutable object was serialized, its raw bytes could be modified so that upon deserialization the object is no longer the same. This can’t be prevented completely. Encryption, checksums, and CRC’s will help to prevent this though. You should read Effective Java written by Joshua Bloch.
Why is serialization required?
Serialization is usually used When the need arises to send your data over network or stored in files. By data I mean objects and not text. … Serialization is the translation of your Java object’s values/states to bytes to send it over network or save it.