CORE JAVA FAQS

6. What is a transient variable?

o The variable, which cannot be serialized, is known as transient variable.


7. What are wrapped classes?

o Wrapped classes are classes that allow primitive types to be accessed as objects.


8. What is an immutable object and what are its advantages?

· An immutable object is an object and any object it references that does not change after construction. The object is, therefore, immutable for its lifetime.

· Immutable classes are commonly used to represent strings, colors, and numeric values.
Advantage:

· They guarantee that their state cannot change after construction, they are inherently thread-safe.


9. What are basic rules, which govern creation of immutable classes?

· Declare the class final.

· Declare all data private.

· Provide only getter methods and no setter methods.

· Set all instance data in the constructor.

· Clone mutable objects for which a reference to them is returned.

· Clone mutable objects for which a reference to them is received.

· Implement a deep clone if the default shallow clone is not correct for a properly behaved immutable object.



10. What is a Java package and how is it used?

· A Java package is a naming context for classes and interfaces. A package is used to create a separate name space for groups of classes and interfaces. Packages are also used to organize related classes and interfaces into a single API unit and to control accessibility to these classes and interfaces