Interview Questions - Java Basics

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.

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.

What are wrapper classes?

Java provides specialized classes corresponding to each of the primitive data types. These are called wrapper classes.

They are example: Integer, Character, Double etc.

Why do we need wrapper classes?

It is sometimes easier to deal with primitives as objects. Moreover most of the collection classes store objects and not primitive data types. And also the wrapper classes provide many utility methods also.

Because of these resons we need wrapper classes. And since we create instances of these classes we can store them in any of the collection classes and pass them around as a collection. Also we can pass them around as method parameters where a method expects an object.