Interview Question and Answers | Search Coding Interview Questions

Interview Questions and Answers - Order By Rating

Q2791. What will happen if class implement two interface having common method?

Ans. That would not be a problem as both are specifying the contract that implement class has to follow.
If class C implement interface A & interface B then Class C thing I need to implement print() because of interface A then again Class think I need to implement print() again because of interface B, it sees that there is already a method called test() implemented so it's satisfied.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops interfaces multiple inheritance}

Q2792. What is the advantage of using arrays over variables ?

Ans. Arrays provide a structure wherein multiple values can be accessed using single reference and index. This helps in iterating over the values using loops.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java arrays loops variables basic interview question}

Q2793. What are the disadvantages of using arrays ?

Core Java

Ans. Arrays are of fixed size and have to reserve memory prior to use. Hence if we don't know size in advance arrays are not recommended to use.

Arrays can store only homogeneous elements.

Arrays store its values in contentious memory location. Not suitable if the content is too large and needs to be distributed in memory.

There is no underlying data structure for arrays and no ready made method support for arrays, for every requriment we need to code explicitly

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java arrays disadvantages of arrays arrays memory arrays vs variables}

Q2794. Difference between Class#getInstance() and new operator ?

Ans. Class.getInstance doesn't call the constructor whereas if we create an object using new operator , we need to have a matching constructor or copiler should provide a default constructor.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java constructor object creation default constructor getinstance new operator}

Q2795. Can we create an object if a Class doesn't have any constructor ( not even the default provided by constructor ) ?

Ans. Yes , using Class.getInstance.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops constructor default constructor class.getinstance}

Q2796. What is a cloneable interface and what all methods does it contain?

Core Java

Ans. Cloneable is a declaration that the class implementing it allows cloning or bitwise copy of it's object state. It is not having any method because it is a MARKER interface.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops cloneable marker interface cloning Asked in 2 Companies}

Q2797. When you will synchronize a piece of your code?

Ans. When you expect your code will be accessed by different threads and these threads may change a particular data causing data corruption.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java threads multi threading synchronization concurrency basic frequent}

Q2798. Are there any global variables in Java, which can be accessed by other part of your program?

Ans. No. Global variables are not allowed as it wont fit good with the concept of encapsulation.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java variables global variables yes no}

Q2799. What is an applet? What is the lifecycle of an applet?

Ans. Applet is a dynamic and interactive program that runs inside a web page displayed by a java capable browser.

Lifecycle methods of Applet -

init( ) method - Can be called when an applet is first loaded
start( ) method - Can be called each time an applet is started
paint( ) method - Can be called when the applet is minimized or maximized
stop( ) method - Can be used when the browser moves off the applet's page
destroy( ) method - Can be called when the browser is finished with the applet

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java ui applet swing awt lifecycle of applet technologies}

Q2800. What is meant by controls and what are different types of controls in AWT / SWT?

Ans. Controls are components that allow a user to interact with your application and SWT / AWT supports the following types of controls:

Labels, Push Buttons, Check Boxes, Choice Lists, Lists, Scrollbars, Text Components.

These controls are subclasses of Component.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java ui swt awt types of controls}

Q2801. What is a stream and what are the types of Streams and classes of the Streams?

Core Java

Ans. A Stream is an abstraction that either produces or consumes information. There are two types of Streams :

Byte Streams: Provide a convenient means for handling input and output of bytes.

Character Streams: Provide a convenient means for handling input & output of characters.

Byte Streams classes: Are defined by using two abstract classes, namely InputStream and OutputStream.

Character Streams classes: Are defined by using two abstract classes, namely Reader and Writer.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java file io streams byte stream character stream file handling Asked in 3 Companies}

Q2802. What is session tracking and how do you track a user session in servlets?

Java EE

Ans. Session tracking is a mechanism that servlets use to maintain state about a series requests from the same user across some period of time. The methods used for session tracking are:

User Authentication - occurs when a web server restricts access to some of its resources to only those clients that log in using a recognized username and password

Hidden form fields - fields are added to an HTML form that are not displayed in the client's browser. When the form containing the fields is submitted, the fields are sent back to the server

URL rewriting - every URL that the user clicks on is dynamically modified or rewritten to include extra information. The extra information can be in the form of extra path information, added parameters or some custom, server-specific URL change.

Cookies - a bit of information that is sent by a web server to a browser and which can later be read back from that browser.

HttpSession- places a limit on the number of sessions that can exist in memory.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve j2ee servlets session session management web applications cookies httpsession url rewriting architecture Asked in 1 Companies}

Q2803. What is connection pooling?

Database

Ans. It's a technique to allow multiple clients to make use of a cached set of shared and reusable connection objects providing access to a database or other resource.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java jdbc db connectivity connection pooling architecture Asked in 3 Companies basic frequent}

Q2804. Advantage of Collection classes over Arrays ?

Core Java

Ans. Collections are re-sizable in nature. We can increase or decrease the size as per recruitment.
Collections can hold both homogeneous and heterogeneous data's.
Every collection follows some standard data structures.
Collection provides many useful built in methods for traversing,sorting and search.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java collections collections classes advantages of collections over arrays collections vs arrays basic interview question Asked in 6 Companies basic frequent}

Q2805. What are the Disadvantages of using Collection Classes over Arrays ?

Core Java

Ans. Collections can only hold objects, It can't hold primitive data types.

Collections have performance overheads as they deal with objects and offer dynamic memory expansion. This dynamic expansion could be a bigger overhead if the collection class needs consecutive memory location like Vectors.

Collections doesn't allow modification while traversal as it may lead to concurrentModificationException.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java collections collections classes disadvantages of collections over arrays collections vs arrays}

Q2806. Can we call constructor explicitly ?

Ans. Yes.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java constructor constructor chaining oops call constructor explicitly yes-no}

Try 1 Question(s) Test

Q2807. Does a class inherit the constructor of its super class?

Ans. No.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops constructor inheritence constructor inheritance yes no}

Q2808. What is the difference between float and double?

Ans. Float can represent up to 7 digits accurately after decimal point, where as double can represent up to 15 digits accurately after decimal point.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types float double difference between basic interview question}

Q2809. What is the difference between >> and >>>?

Ans. Both bitwise right shift operator ( >> ) and bitwise zero fill right shift operator ( >>> ) are used to shift the bits towards right. The difference is that >> will protect the sign bit whereas the >>> operator will not protect the sign bit. It always fills 0 in the sign bit.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java operators bitwise operators binary shift right shift}

Q2810. What is the difference between System.out ,System.err and System.in?

Ans. System.out and System.err both represent the monitor by default and hence can be used to send data or results to the monitor. But System.out is used to display normal messages and results whereas System.err is used to display error messages and System.in represents InputStream object, which by default represents standard input device, i.e., keyboard.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java io system.out system.err system.in difference between advanced basic interview question}

Q2811. Is it possible to compile and run a Java program without writing main( ) method?

Ans. Yes, it is possible by using a static block in the Java program.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java main static block compile yes-no}

Frequently asked in Infosys and HCL Technologies ( Based on 2 feedback )

Q2812. What are different ways of object creation in Java ?

Core Java

Ans. Using new operator - new xyzClass()

Using factory methods - xyzFactory.getInstance( )

Using newInstance( ) method - (Class.forName(xyzClass))emp.newInstance( )

By cloning an already available object - (xyzClass)obj1.clone( )

Sample Code for object initialization using clone

Sample Code for object initialization using getInstance

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops object creation new operator class.forname cloning ebay Asked in 9 Companies expert}

Q2813. What is Generalization and Specialization in terms of casting ?

Core Java

Ans. Generalization or UpCasting is a phenomenon where a sub class is prompted to a super class, and hence becomes more general. Generalization needs widening or up-casting. Specialization or DownCasting is a phenomenon where a super class is narrowed down to a sub class. Specialization needs narrowing or down-casting.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types casting type casting up casting type casting downcasting type casting generalization specialization Asked in 2 Companies}

Q2814. Can we call the garbage collector explicitly ?

Core Java

Ans. Yes, We can call garbage collector directly but it doesn't guarantees that the gc will start executing immediately. This gc( ) method appears in both Runtime and System classes of java.lang package.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java garbage collection java memory management jvm gc yes no Asked in 4 Companies expert}

Try 1 Question(s) Test

Advanced level question usually asked to senior developers , leads and architects.

Q2815. How does volatile affect code optimization by compiler?

Core Java

Ans. Volatile is an instruction that the variables can be accessed by multiple threads and hence shouldn't be cached. As volatile variables are never cached and hence their retrieval cannot be optimized.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java keywords volatile synchronization compiler optimization variable caching architecture Asked in 3 Companies expert}

Q2816. Do you think that Java should have had pointers ?

Core Java

Ans. Open ended Questions.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java open questions pointers advanced}

Q2817. How would you go about debugging a NullPointerException?

Core Java

Ans. Open ended Questions.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java open questions exceptions}

Q2818. How does Java differ from other programming languages you've worked with?

Ans. Open ended Questions.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java open questions}

Q2819. Should good code be self-documenting, or is it the responsibility of the developer to document it?

Process

Ans. Open ended Questions.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java open questions code review documentation clean code}

Q2820. What are points to consider in terms of access modifier when we are overriding any method?

Core Java

Ans. 1. Overriding method can not be more restrictive than the overridden method.

reason : in case of polymorphism , at object creation jvm look for actual runtime object. jvm does not look for reference type and while calling methods it look for overridden method.

If by means subclass were allowed to change the access modifier on the overriding method, then suddenly at runtime when the JVM invokes the true objects version of the method rather than the reference types version then it will be problematic

2. In case of subclass and superclass define in different package, we can override only those method which have public or protected access.

3. We can not override any private method because private methods can not be inherited and if method can not be inherited then method can not be overridden.

Sample Code for Overriding

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java overriding access specifier inheritence oops polymorphism object oriented programming (oops) oops concepts runtime polymorphism object oriented programming (oops) oops concepts Asked in 4 Companies}

Try 2 Question(s) Test

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.