Recent - JAVA Interview Questions & Answers

Q : What is the difference between Java platform and other platforms?
A : The Java platform differs from most other platforms in that it's a software-only platform that runs on top of other hardware-based platforms.

The Java platform has two components:

1. The Java Virtual Machine (Java VM)

2. The Java Application Programming Interface (Java API)

Q : What is Java Virtual Machine?

A : The Java Virtual Machine is a software that can be ported onto the various hardware-based platforms.

Q : What is the package? Define with an example?

A : A package is a grouping of related types providing access protection and name space management. Note that types refers to classes, interfaces, enumerations, and annotation types. Enumerations and annotation types are special kinds of classes and interfaces, respectively, so types are often referred to in this lesson simply as classes and interfaces.

Package is a directory of related classes and interfaces.
Eg: java.lang.*

Here java is a directory,lang stands for language & it is a sub directory, * indicates collection of related classes & interfaces

Q : What is the difference between the interface and abstract class?
A : An abstract class may contain code in method bodies, which is not allowed in an interface. With abstract classes, you have to inherit your class from it and Java does not allow multiple inheritance. On the other hand, you can implement multiple interfaces in your class.

Q : What is the thread?
A : A thread is an independent path of execution in a system.

Q :What is the multi-threading?
A: Multi-threading means various threads that runs in a system.

Q : What is the synchronization ? why is it important in Java Programming?
A : With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is an possible for one thread to modify a shared object while another thread is in the process of using or updating that object’s value. This often causes dirty data and leads to significant errors.

Q : What is the purpose of Runtime class in Java Programming?
A :The purpose of Runtime class is to provide access to the Java runtime system in Java Programming.

Q :Describe difference between a static and a non-static inner class in Java Programming?
A non-static inner class may have object instances that are associated with instances of the class’s outer class. A static inner class does not have any other object instances.

Q : Name the primitive Java types?
A : The primitive types are,

byte, char, short, int, long, float, double, and boolean.

Q : What is the casting in Java Programming?
A : There are two types of casting, casting between primitive numeric types and casting between object references.
Casting between numeric types is used to convert larger values, such as double values, to smaller values, such as byte values. Casting between object references is used to refer the object by a compatible class, interface, or array type reference.

Q : What are the Encapsulation, Inheritance and Polymorphism?
A : Encapsulation is the mechanism that binds together code and data it manipulates and keeps both safe from outside interference and misuse.
Inheritance is the process by which one object acquires the properties of another object. Polymorphism is the feature that allows one interface to be used for general class actions.

Q : What is the difference between constructor and method?
A : Constructor will be automatically invoked when an object is created where as the method has to be called explicitly.

Q: What is a UNICODE?-
A : A Unicode is used for internal representation of characters and strings and it uses 16 bits to represent each other.

Q : What is a abstract class?
A :A abstract class is a class designed with implementation gaps for subclasses to fill in and is deliberately incomplete.

Q : What is daemon thread ? which the method is used to create the daemon thread?-
A: Daemon thread is a low priority thread which runs intermittently in the back ground doing the garbage collection operation for the java runtime system.

SetDaemon method is used to create a daemon thread.

Q: What are the wrapper classes?
A : The Wrapper classes are classes that allow primitive types to be accessed as objects.

Q : What is the difference between applet and a servlet?
A : Servlets are to servers what applets are to browsers.
Applets must have graphical user interfaces whereas servlets have no graphical user interfaces.

Q :What are the cookies ?
A : Cookies are a mechanism that a servlet uses to have a client hold a small amount of state-information associated with the user.

Q :What is Java Bean?
A : Java Bean is a software component that has been designed to be reusable in a variety of different environments.

J2EE Interview questions & answers

Q : what is J2EE ?what is the features?
J2EE is java to enterprise edition. It is used to develop web applications

Q : Define Hash table?
Hash tables are good for doing a quick search on things.
For instance if we have an array full of data (say 100 items).If we known the position that a specific item is stored in an array, then we could quickly access it. For instance, we just happen to know that the item we want it is at position 3; I can apply:
myitem=myarray[3];
There are many different hash functions. Some hash functions will take an integer key and turn it into an index. A common one is used to the division method

Q : what is the difference between web server & application server ?
A : web server can have only the web container. But Application server can have web container as well as EJB container
Example of Application Server : JBOSS
Web Server : TOMCAT.

Q : What are the components of J2EE application?
A : A J2EE component is a self-contained functional software unit that is assembled into a J2EE application with its related classes and files and communicates with other components. The J2EE specification defines the following J2EE components:
Application clients and applets are client components.
Java Servlet and JavaServer PagesTM (JSPTM) technology components are web components.
Enterprise JavaBeansTM (EJBTM) components (enterprise beans) are business components.
Resource adapter components provided by EIS and tool vendors

Q : What is a J2EE component ?
A : A self-contained functional software unit supported by the container and configurable at deployment time. The J2EE specification defines the following J2EE components: Application clients and applets are components that run on the client. Java servlet and JavaServer Pages (JSP) technology components are Web components that run on the server. Enterprise JavaBeans (EJB) components (enterprise beans) are business components that run on the server. J2EE components are written in the Java programming language and are compiled in the same way as any program in the language. The difference between J2EE components and "standard" Java classes is that J2EE components are assembled into a J2EE application, verified to be well formed and in compliance with a J2EE specification, and deployed to production, where they are run and managed by the J2EE server or client container.

Q : What is "applet"?
A: A J2EE component that is a typically executes in a Web browser but can execute in a variety of other applications or devices that support the applet programming model.

Q : Difference between RMI and EJB?
A : EJB uses RMI technology.
We have to declare the middleware services needed by the EJB in a descriptor.
The Applet server will generate stubs for the same.

RMI : one has to write the middleware services. (txn mgmt, persitence.)

EJB cannot be invoked directly by the remote clients because there are not network enabled.
Location transparency.

Q : What is a web container?
A :Runtime environment for servlets and JSP
Manages lifecycle of instances
Supports HTTP

Q : What’s the difference between URL Connection instance and URL instance?
A : URL Connection instance represents a link for accessing or communicating with the resource at the location and a URL instance represents the location of a resource.

Q :What technologies are included in J2EE?
A :The primary technologies in J2EE are: Enterprise JavaBeansTM (EJBsTM), JavaServer PagesTM (JSPsTM), Java Servlets, the Java Naming and Directory InterfaceTM (JNDITM), the Java Transaction API (JTA), CORBA, and the JDBCTM data access API.

Q : What is XLink ?
A : The part of the XLL specification that is concerned with the specifying links between documents.

Q : What is XLL ?
A : The XML Link Language specification, consisting of XLink and XPointer.

Q : What is in-memory replication?
A : The process by which the contents in the memory of one physical m/c is replicated in all the m/c in the cluster is called in-memory replication.
Q : What is a JavaBeans component
A : A JavaBeans class that can be manipulated by tools and composed into the applications. A JavaBeans component must adhere to the certain property and event interface conventions.

Q : What is the J2EE module?
A : The J2EE module consists of one or more J2EE components.For the same container type and one component deployment descriptor of that type

Q : What is a Web resource ?
A static or dynamic object contained in a Web application that can be referenced by a Uniform Resource Locator URL.

Q : What is "application assembler"?
A : A person who combines J2EE components and modules into deployable application units.

Q : What are the four types of J2EE modules?
A : The four types of J2EE modules are
• Application client module
• Web module
• Enterprise JavaBeans module
• Resource adapter module

XML Interview Questions & Answers

Q : How can u create an XML file?
A : It is a quite easy to create, can create by the plain text editor like notepad or by .net model using so many in built methods like XmlTextWriter etc.

Q : What is a XML Namespace?
A : Defining a namespace to avoid the confusion involves using a prefix and adding an xmlns attribute to the tag to give the prefix a qualified name associated with the namespace. All the child elements with the same prefix are associated with the namespace defined in the start tag of an element.

Q : What’s the difference between SAX parser and DOM parser?
A : SAX parser - works incrementally and generate the events that are passed to the application. It does not generate data representation of xml content so some programming is required. However, it provides the stream processing and partial processing which cannot be done alone by DOM parser.
DOM parser - reads the whole XML document and returns a DOM tree representation of xml document. It provides a convenient way for reading, analyzing and manipulating XML files. It is not well a suited for the large xml files, as it always reads the whole file before processing.

Q : Describe the differences between XML and HTML?
A : XML :
• User definable tags
• Content driven End tags required for well formed documents
• Quotes required around attributes values
• Slash required in empty tags

HTML :
• Defined set of tags designed for web display
• Format driven
• End tags not required
• Quotes not required
• Slash not required

Q : What is DOM?
A : The Document Object Model (DOM) is an interface specification maintained by the W3C DOM Workgroup that defines is an application independent mechanism
to access, parse, or update XML data. In the simple terms it is a hierarchical model that allows developers to manipulate XML documents easily.

Q :Why is XML such an important development?
A : XML removes the two constraints which were holding the back Web developments: dependence on a single, inflexible document type (HTML); the complexity of full SGML.

Q : What is a XPointer?
A : XPointer is a set of recommendations developed by the W3C. The core recommendations are the XPointer Framework which provides an extensible addressing behavior for fragment identifiers in XML media types.
XPointer gains its extensibility through the XPointer Framework, which identifies the syntax and processing architecture for XPointer expressions and through an extensible set of XPointer addressing schemes. These schemes, e.g., element() or xpointer(), are actually QNames. The xmlns() scheme makes it possible for an XPointer to declare namespace bindings and thereby the use third-party schemes as readily as W3C defined XPointer schemes.

Q : What is the three essential components of security does the XML Signatures provide?
A : Authentication, message integrity, and non-repudiation. In addition to signature information, an XML Signature can also contain the information describing the key used to sign the content.

Q :What’s an XML namespace prefix?
A : An XML namespace prefix is a prefix used to specify that a local element type or attribute name is in a particular XML namespace.

Q : Why is XML such an important development?
A : XML removes the two constraints which were holding back Web developments:
1. Dependence on a single, inflexible document type (HTML) which was being much abused for tasks it was never designed for;
2. The complexity of full SGML, whose syntax allows many powerful but hard-to-program options.
XML allows the flexible development of user-defined document types. It provides a robust, non-proprietary, persistent, and verifiable file format for the storage and the transmission of text and data both on and off the Web, and it’s remove the more complex options of SGML, making it easier to program for.

J2ME Interview Questions & Answers

Q : What is J2ME ?
A : Java 2 Micro Edition(J2ME) is a group of specifications and technologies that pertain to Java on small devices. The J2ME moniker covers a wide range of devices, from the pagers and mobile telephones through the set-top boxes and car navigation systems. The J2ME world is divided into the configurations and profiles, specifications that describe a Java environment for a specific class of device.

Q : What is the Generic Connection Framework ?
A : The Generic Connection Framework (GCF) makes it is very easy for wireless devices to make the network connections. It is part of a CLDC and CDC and resides in the javax.microedition.io package.

Q : What is a RMI ?
A : Remote method invocation (RMI) is a feature of J2SE that enables to the Java objects running in one virtual machine to invoke the methods of Java objects running in another virtual machine, seamlessly.

Q : What’s WDP?
A : Wireless Datagram Protocol (WDP)is worked as the transport layer of WAP. WDP processes datagrams from the upper layers to formats required by the different physical datapaths like GSM SMS or CDMA Packet Data. WDP is adapted to the bearers available in the device so upper layers do not need to the care about the physical level.

Q : What is JCP ?
A : The Java Community Process (JCP) is an open the organization of international Java developers and licensees who develop and revise Java technology specifications, reference the implementations, and technology compatibility kits through a formal process.

Q : What is a OTA ?
A : Over The Air (OTA) refers to any the wireless networking technology.

Q : What is kXML ?
A : The kXML project provides a small of footprint XML parser that can be used with the J2ME.

Q : What is PCS ?
A : Personal Communications Service (PCS) is a suite of second-generation, digitally modulated mobile-communications the interfaces that includes TDMA, CDMA, and GSM. PCS serves as an umbrella term for the second-generation wireless technologies operating in the 1900MHz range.

Q :What is the Personal Profile ?

A The Personal Profile is a J2ME profile the specification. Layered on the Foundation Profile and CDC, the Personal Profile will be the next generation of PersonalJava technology. The specification is currently in development under the Java Community Process (JCP).

Q : What is TDMA ?
A: Time Division Multiple Access (TDMA) is a second-generation modulation standard using bandwidth the allocated in the 800 MHz, 900 MHz, and 1900MHz ranges.

Q : What is WTLS ?
A : Wireless Transport Layer Security protocal (WTLS) does all cryptography oriented features of WAP. WTLS handles encryption/decryption, user authentication and data integrity. WTLS is based on the fixed network Transport Layer Security protocal (TLS), formerly known as Secure Sockets Layer (SSL).

Q : What ‘s WTP ?
A : Wireless Transaction Protocol (WTP) is WAP's transaction protocol that works between the session protocol WSP and security protocol WTLS. WTP chops data packets into lower level datagrams and concatenates received datagrams into useful data. WTP also keeps track of received and sent packets and does re-transmissions and acknowledgment sending when needed.

Q : What is WMLScript
A : WMLScript is a subset of the JavaScript scripting language designed to as part of the WAP standard to provide a convenient mechanism to access the mobile phone's peripheral functions.

Recent C++ Interview questions & Answers

Q : Explain in void pointer using C++?
A : In C++, void represents the absence of type, so void the pointers are pointers that point to a value that has no type. The void pointers can point to any data type.
We can declare void pointer as follows.
Void *p;

Q : What is the function overloading in C++?
A : You can have the multiple functions with same name using function overloading facility of C++. You can use same name for multiple functions when all these functions are doing same thing.

Q : What is virtual function?
Answer - Virtual function is the member function of a class that can be overridden in its derived class. It is declared with virtual keyword. Virtual function call is resolved at run-time (dynamic binding) whereas the non-virtual member functions are resolved at compile time (static binding).

Q : What is Null object in C++?
A : Null Object is an object of some class whose purpose is to indicate that a real object of that class does not exist. One common use for a null object is a return value from a member of function that is supposed to return an object with some specified properties but cannot find such an object.

Q : What is virtual function? where is it used?
A : Virtual function is a member of function that is declared by with in a base class and redefined by the derived class. to make a function virtual prefix the function name by the "virtual" keyword. It helps in polymorphism.

Q : what is a template
A template function defines a set of operations to performed on the various data types This data is passed to the function as an argument

Q : What do you mean by the inheritance?
A : The Inheritance is the process by which one can aquire the properties of another object

Q : Explain the scope resolution operator?
A: The scope resolution operator is a permits of a program to reference an identifier in the global scope that has been hidden by another identifier with the same name in the local scope.

Q : What is parameterized type?
A : : A template is a parameterized construct or type containing the generic code that can use or manipulate any type. It is called the parameterized because an actual type is a parameter of the code body. Polymorphism may be achieved through parameterized types. This type of polymorphism is called parameteric polymorphism. Parameteric polymorphism is the mechanism by which the same code is used on different types passed as parameters.

Q : Explain the scope resolution operator?
A :Resolution operator permits a program to reference an identifier in the global scope that has been hidden by another identifier with the same name in the local scope.

Q : Name of the some pure object oriented languages?
A : Some pure object oriented languages are
• Smalltalk,
• Java,
• Eiffel,
• Sather.

Q : Differentiate between a C++ struct and C++ class?
A : The default member and base-class access specifies are different. This is one of the commonly misunderstood aspects of C++. Believe it is or not, many programmers think that a C++ struct is just like a C struct, while a C++ class has inheritance, access specifies, member functions, overloaded operators, and so on. Actually, the C++ struct has all the features of the class. The only differences are that a struct defaults to public member access and public base-class inheritance, and a class defaults to the private access specified and private base-class inheritance.

Q : Why do C++ compilers need the name mangling?
A : Name mangling is the rule of according to which is the C++ changes function's name into function signature before the passing that the function to a linker. This is how the linker differentiates between different functions with the same name.

Q : What is protocol class?
A : An abstract class is a protocol class if:
1.Protocol neither contains nor inherits from the classes that contain member data, non-virtual functions, or private (or protected) members of any kind.
2. It has a non-inline virtual destructor defined with an empty implementation,
3. All member functions other than the destructor including inherited functions, are declared pure the virtual functions and left undefined.

Q : What is the difference between the message and method?
A: Method: Provides response to a message.It is an implementation of an operation..
Message: Objects communicate by sending the messages to each other.A message is sent to invoke a method.]

Q : What is an adaptor class ?
A : A class that has no functionality of its own. It is the member functions hide the use of a third party software component or an object with the non-compatible interface or a non- object- oriented implementation.

Q : What’s the difference between char a[] = “string”; and char *p = “string”;?
A : In the first case six bytes are allocated to the variable in a which is fixed, where as in the second case if *p is assigned to the some other value the allocate memory can change.

Q : What is conversion constructor?
A : A conversion constructor is that accepts one argument of a different type.

Q : What’s an explicit constructor?
A : A conversion constructor declared with the explicit keyword. The compiler does’nt use an explicit constructor to implement an implied conversion of types. It is the purpose of is reserved explicitly for construction.

C++ Interview Questions & Answers

Q : How do youn delete an element in array of string?

A : Reduce the array size.

if(stringarryname)

{

delete[] stringarryname;

delete stringarryname;

stringarryname = NULL;

}


Q : What is the difference between an overload assignment operator and an a copy constructor?

A :. An overloaded assignment operator assigns the contents of an existing object to another existing object of the same class. A copy constructor constructs a new object by using the content of the argument object


Q :What is the virtual destructor?

A : The virtual destructor is one that is declared with the virtual attribute.

The behavior of a virtual destructor is what is important. If you destroy an object through a baler or reference to a base class, and the base-class destructor is not virtual, the derived-class destructors are not executed, and the destruction might not be compile.

Q: What is the Difference between C and C ++?

A : C is a structured programming language. The C++ is an object oriented language. C++ is also called as C with Classes.

both C and C++ are programming languages. C++ is termed as superset of C.
C is a powerful and elegent language.almost all c PROGRAMS ARE ALSO c++ PROGRAMS. C, it facilitates--" topdown structured design" as against C++ provides bottom-up object-oriented design. C language is built from functions (like printf)that execute different tasks.

Q : Difference between a template class and class template in C++?

A : Template class: A generic definition or a parametrized class not instantiated until the client provides the needed information. It is the jargon for plain templates.
Class template: A class template specifies how individual classes can be constructed much like the way a class specifies how individual objects can be constructed. It is jargon for plain classes.

Q : What is the polymorphism in C++?

A : Polymorphism in the C++ is the idea that a base class can be inherited by several classes. A base class pointer can point to its child class and base class array can store different child class objects.

Recent Data Structure Interview Questions & Answers

Q : What’s the purpose of a left child node and a right child node?
A : The left child node and right child node helps in sorting technology because parent will be having larger value than that of left and left child will be having larger value than that of right.

Q : What is the advantage of using a queue linked list?
A : The Most Important is CPU Scheduling , refers a Queue for scheduling.
Queue is to Faster then Other One(stack)

Q : What is linked list?
A : Linked list is a data structure which is contain the data elements and a pointer of the node type of which points to the next node in the linked list. It is useful when you do not know in advance how many elements will be there so you cannot pre allocate space (e.g. using an array).

Q : Which data structure is used to perform the recursion?
A : Stack has the LIFO (Last In First Out) property; it remembers it is a ‘caller’. Therefore, it knows as to whom it should return when the function has to return. On the other hand, recursion makes use of the system stack for storing the return addresses of the function calls. Every recursive function has its equivalent iterative (non-recursive) function. Even when such the equivalent is iterative procedures are written explicit, stack is to be used.

Q : What are some of the applications for the tree data structure?
A : There are three types of the application for the tree data structure,
• Symbol table construction.
• Manipulation of the arithmetic expressions.
• Syntax analysis

Q : What is spanning Tree?
A : A spanning tree is a tree associated with a network. All the nodes are the graph appear on the tree once. A minimum spanning tree is a spanning tree organized so that the total edge weight between nodes is minimized.

Q : What’s the difference between STACK and ARRAY?
A : In array the items can be entered or removed in any order. Basically each member access is done using the index. No strict order is to be followed here to remove a particular element. STACK follows LIFO. Thus the item that is first entered would be the last removed.

Q : What is the method removes the value from the top of a stack?
A : The pop() member method removes the value from the top of a stack, which is then returned by the pop() member method to the statement that is called the pop() member method.

Q : What is queue ?
A : A Queue is a sequential organization of data. A queue is a FIFO type of data structure. An element is an inserted at the last position and an element is always taken out from the first position.

Q : Difference between malloc and calloc ?
A : calloc: allocate the m times n bytes initialized to 0
malloc: allocate the n bytes.

Q : what is an abstract data type?
A : Abstract data type is a logical cohesion of operands or variables along with a set of operation which can be performed on it. In Java we have most of data types as abstract data types. It helps in implementing the oops concept of encapsulation, abstraction, modularisation. Eg :String data type in java is an abstract data type. String is defined as a character array data member of a class All operations related to or which can be performed on strings are included as methods of the class.

Q : What’s the difference between bubble sort & quick sort?
A : Bubble sort is a very easy to program, slower, iterative. Compares neighboring numbers swaps it if required and continues this procedure until there are no more swaps
Quick Sort is a little difficult to program, Fastest, Recursive. Pivot number is selected, other numbers are compared with it and shifted to the right of number or left depending upon criteria again this method is applied to the left and right list generated to the pivot point number. Select pivot point among that the list.

Q : What is linear and non-linear data structures?
A : Linear data structure is an array, linked list
Non linear data structure is a tree, graph

Q : What is user-defined data type?
A : A user defined data type is a structure of which contains variables of basic data types.
For (ex) user can define a data type called employee which contains variables like string EmpName, int DeptNo, float Salary etc.