JAVA Interview Questions Page4

What is the primary benefit of Encapsulation?

The main benefit of encapsulation is the ability to modify our implemented code without breaking the code of others who use our code. With this Encapsulation gives maintainability, flexibility and extensibility to our code.

What is an Interface?

An interface is a collection of abstract methods. A class implements an interface, thereby inheriting the abstract methods of the interface.

Give some features of Interface?

It includes −

• Interface cannot be instantiated
• An interface does not contain any constructors.
• All of the methods in an interface are abstract.

Define Packages in Java?

A Package can be defined as a grouping of related types(classes, interfaces, enumerations and annotations ) providing access protection and name space management.

Why Packages are used?

Packages are used in Java in-order to prevent naming conflicts, to control access, to make searching/locating and usage of classes, interfaces, enumerations and annotations, etc., easier.

What do you mean by Multithreaded program?

A multithreaded program contains two or more parts that can run concurrently. Each part of such a program is called a thread, and each thread defines a separate path of execution.

What are the two ways in which Thread can be created?

Thread can be created by: implementing Runnable interface, extending the Thread class.

What is an applet?

An applet is a Java program that runs in a Web browser. An applet can be a fully functional Java application because it has the entire Java API at its disposal.

An applet extend which class?

An applet extends java.applet.Applet class.

Explain garbage collection in Java?

It uses garbage collection to free the memory. By cleaning those objects that is no longer reference by any of the program.

Define immutable object?

An immutable object can’t be changed once it is created.

Explain the usage of this() with constructors?

It is used with variables or methods and used to call constructer of same class.

Explain Set Interface?

It is a collection of element which cannot contain duplicate elements. The Set interface contains only methods inherited from Collection and adds the restriction that duplicate elements are prohibited.

Explain TreeSet?

It is a Set implemented when we want elements in a sorted order.

What is Comparable Interface?

It is used to sort collections and arrays of objects using the collections.sort() and java.utils. The objects of the class implementing the Comparable interface can be ordered.

Difference between throw and throws?

It includes:

• Throw is used to trigger an exception where as throws is used in declaration of exception.
• Without throws, Checked exception cannot be handled where as checked exception can be propagated with throws.