Java Questions

A JAR file (short for Java Archive) is a ZIP file used to distribute a set of Java classes. It is used to store compiled Java classes and associated metadata that can constitute a program

1.Main difference is methods of a Java interface are implicitly abstract and cannot have implementations. A Java abstract class can have instance methods that implements a default behavior.

2.Variables declared in a Java interface is by default final. An abstract class may contain non-final variables.

3.Members of a Java interface are public by default. A Java abstract class can have the usual flavors of class members like private, protected, etc..

4.Java interface should be implemented using keyword “implements”; A Java abstract class should be extended using keyword “extends”.

5.An interface can extend another Java interface only, an abstract class can extend another Java class and implement multiple Java interfaces.

6.A Java class can implement multiple interfaces but it can extend only one abstract class.

7.Interface is absolutely abstract and cannot be instantiated; A Java abstract class also cannot be instantiated, but can be invoked if a main() exists.

8.In comparison with java abstract classes, java interfaces are slow as it requires extra indirection.

The Spring IoC is responsible for creating the objects,managing them (with dependency injection (DI)), wiring them together, configuring them, as also managing their complete lifecycle.

Unwrapping is also called as unpacking or unboxing.

Getting the private data stored in the object by using methods is called unpacking or unwrapping.

The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources can be reclaimed and reused. A Java object is subject to garbage collection when it becomes unreachable to the program in which it is used.

Cloning refers to creating duplicate copies of objects in java.

Shallow Cloning: Shallow cloning is a bitwise copy of an object. New object is created which is an exact copy that of the original one. In case any objects are referring the fields of these objects, just the references are copied.

Deep Cloning: In deep cloning, complete duplicate copy of the original copy is created. Deep cloning creates not only the primitive values of the original objects but also copies all its sub objects as well.

Clonable interface is used to perform cloning in java.