Java Basics - Interview Questions and Answers

  1. What is the common usage of serialization?
    Whenever an object is to be sent over the network, objects need to be serialized. Moreover if the state of an object is to be saved, objects need to be serilazed.
  2. What is Externalizable interface?

    Externalizable is an interface which contains two methods readExternal and writeExternal. These methods give you a control over the serialization mechanism.

    Thus if your class implements this interface, you can customize the serialization process by implementing these methods.

  3. When you serialize an object, what happens to the object references included in the object?

    The serialization mechanism generates an object graph for serialization. Thus it determines whether the included object references are serializable or not. This is a recursive process.

    Thus when an object is serialized, all the included objects are also serialized alongwith the original obect.

  4. What one should take care of while serializing the object?
    One should make sure that all the included objects are also serializable. If any of the objects is not serializable then it throws a NotSerializableException.
  5. What happens to the static fields of a class during serialization?

    There are three exceptions in which serialization doesnot necessarily read and write to the stream. These are

    1. Serialization ignores static fields, because they are not part of ay particular state state.

    2. Base class fields are only hendled if the base class itself is serializable.

    3. Transient fields.

  6. Does Java provide any construct to find out the size of an object?
    No, there is not sizeof operator in Java. So there is not direct way to determine the size of an object directly in Java.

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