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| Ans. RMI stands for Remote Method Invocation. Traditional approaches to executing code on other machines across a network have been confusing as well as tedious and error-prone to implement. The nicest way to think about this problem is that some object happens to live on another machine, and that you can send a message to the remote object and get a result as if the object lived on your local machine. This simplification is exactly what Java Remote Method Invocation (RMI) allows you to do. | ||||
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| Ans. The JDBC is a pure Java API used to execute SQL statements. It provides a set of classes and interfaces that can be used by developers to write database applications. The steps needed to execute a SQL query using JDBC: 1. Open a connection to the database. 2. Execute a SQL statement. 3. Process th results. 4. Close the connection to the database. | ||||
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Discuss Correct / Improve java jdbc db connectivity Asked in 2 Companies  basic  frequent | ||||
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| Ans. JSON is "JavaScript Object Notation", primarily used for client-server or server-server communication. Its a much lighter and readable alternative to XML. JSON is language independent and is easily parse-able in all programming languages. | ||||
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| Discuss Correct / Improve json markup language client server communication Asked in 26 Companies basic frequent | ||||
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| Ans. eval | ||||
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| Discuss Correct / Improve json markup language | ||||
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| Ans. Number String Boolean Array Object null | ||||
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| Discuss Correct / Improve json markup language client server communication | ||||
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| Ans. Lighter and faster than XML as on-the-wire data format Object Representation - Information is presented in object notations and hence better understandable. Easy to parse and conversion to objects for information consumption. Support multiple data types - JSON supports string, number, array, boolean whereas XML data are all string. | ||||
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| Discuss Correct / Improve json markup language Asked in 1 Companies intermediate frequent | ||||
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| Ans. clone() - Creates and returns a copy of this object. equals() - Indicates whether some other object is "equal to" this one. finalize() - Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. getClass() - Returns the runtime class of an object. hashCode() - Returns a hash code value for the object. toString() - Returns a string representation of the object. notify(), notifyAll(), and wait() - Play a part in synchronizing the activities of independently running threads in a program. | ||||
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| Ans. JMS Provides high-performance asynchronous messaging. It enables Java EE applications to communicate with non-Java systems on top of various transports. | ||||
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| Discuss Correct / Improve java j2ee jms Asked in 1 Companies | ||||
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| Ans. URL is Uniform Resource Locator which is representation of HTTP address. | ||||
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| Discuss Correct / Improve j2ee http internet url basic rare | ||||
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| Ans. HTTP or Hypertext Transfer Protocol is internet protocol for tranmission of hypertext ( text with meta data ) over internet. | ||||
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| Discuss Correct / Improve j2ee http internet fidelity Asked in 2 Companies basic frequent | ||||
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| Ans. Tomcat is a web server and a Servlet container. It is often used as an application server for web-based applications but does not include the complete suite of capabilities that a Java EE application server would supply. | ||||
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| Discuss Correct / Improve tomcat j2ee web server application server build management | ||||
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| Ans. boolean ---> false byte ----> 0 short ----> 0 int -----> 0 long ------> 0l char -----> /u0000 float ------> 0.0f double ----> 0.0d any object reference ----> null | ||||
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| Discuss Correct / Improve java data types default values | ||||
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| Very frequently asked to Fresh graduates. | ||||
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| Ans. 1.Abstraction solves the problem at design level while encapsulation solves the problem at implementation level 2.Abstraction is used for hiding the unwanted data and giving relevant data. while Encapsulation means hiding the code and data into a single unit to protect the data from outside world. 3. Abstraction lets you focus on what the object does instead of how it does it while Encapsulation means hiding the internal details or mechanics of how an object does something. 4.For example: Outer Look of a Television, like it has a display screen and channel buttons to change channel it explains Abstraction but Inner Implementation detail of a Television how CRT and Display Screen are connect with each other using different circuits , it explains Encapsulation. | ||||
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| Discuss Correct / Improve java oops oops concepts encapsulation object oriented programming (oops) oops concepts abstraction basic interview question encapsulation vs abstraction Asked in 10 Companies basic frequent | ||||
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| Ans. A static initialization block is a normal block of code enclosed in braces, { }, and preceded by the static keyword. Here is an example: static { // whatever code is needed for initialization goes here } A class can have any number of static initialization blocks, and they can appear anywhere in the class body. The runtime system guarantees that static initialization blocks are called in the order that they appear in the source code. | ||||
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| Ans. For top level class we can only use "public" and "default". We can use private with inner class. | ||||
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| Discuss Correct / Improve java class access specifier inner classes basic frequent | ||||
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| Ans. An asynchronous event is one that occurs at an unpredictable time outside the control of the program that the CPU is running. It is not "synchronized" with the program. | ||||
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| Ans. Sometime we just need classes or class objects just to be used as part of a particular class or objects. Making them non nested won't make any difference as far as functionality is concerner but making them Nested provide a level of convenience and protection fro, being used anywhere else. Moreover it helps reducing the Code. | ||||
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| Ans. To display the current CLASSPATH variable, use these commands in UNIX (Bourne shell): % echo $CLASSPATH To delete the current contents of the CLASSPATH variable, In UNIX: % unset CLASSPATH; export CLASSPATH To set the CLASSPATH variable, In UNIX: % CLASSPATH=/home/george/java/classes; export CLASSPATH | ||||
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| Ans. Abstract classes are only meant to be sub classed and not meant to be instantiated whereas concrete classes are meant to be instantiated. | ||||
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| Discuss Correct / Improve java oops abstract classes Abstract vs Concrete Class Asked in 1 Companies basic frequent | ||||
| Very Frequently asked to fresh graduates and less experienced. Favorite question in Walk in drives. Frequently asked in Indian Services companies. | ||||
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| Ans. Overloading - Similar Signature but different definition , like function overloading. Overriding - Overriding the Definition of base class in the derived class. | ||||
 Sample Code for overloading Sample Code for overriding | ||||
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| Discuss Correct / Improve java oops overloading overriding oops concepts basic interview question overloading vs overriding Asked in 86 Companies basic frequent | ||||
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| Ans. Vectors are synchronized whereas Array lists are not. | ||||
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| Discuss Correct / Improve java basic interview question vector arraylist collections synchronization vector vs arraylist Asked in 35 Companies basic frequent | ||||
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| Ans. Threads in Java can be implement either by Extending Thread class or implementing runnable interface. | ||||
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| Discuss Correct / Improve java threads multi threading Asked in 1 Companies basic frequent | ||||
| Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM. | ||||
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| Ans. Volatile is a declaration that a variable can be accessed by multiple threads and hence shouldnt be cached. | ||||
| Sample Code for volatile | ||||
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| Discuss Correct / Improve java oops synchronization volatile java keywords Asked in 42 Companies intermediate frequent | ||||
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| Frequently asked in Cognizant (CTS) | ||||
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| Ans. Storing the state of an object in a file or other medium is called serialization. Classes can communicate only if they are built together ( as they need Byte code for communication ). What if we need to enable communication between different applications ( i.e they have been built independently or even they reside at different locations ), We need a mechanism that will transfer the Bean state to a Medium than can be transferred to the receiving application. | ||||
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| Discuss Correct / Improve java oops serialization Asked in 18 Companies basic frequent | ||||
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| Ans. It in Java is used to indicate that a field should not be serialized. | ||||
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| Ans. A Method that cannot be overriden in the sub class. | ||||
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| Discuss Correct / Improve java oops java keywords final final method overriding basic interview question basic frequent | ||||
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| Very Frequently asked.Favorite question in Walk in drive for many Indian service companies. | ||||
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| Ans. A Class that cannot be sub classed. | ||||
| Sample Code for final class | ||||
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| Discuss Correct / Improve java oops final final class java keyword basic interview question Asked in 3 Companies basic frequent | ||||
| Very frequently asked. Usually asked with questions related to String. Frequently asked at CTS / Cognizant | ||||
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| Ans. Object that can't be changed after instantiation. | ||||
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| Discuss Correct / Improve java oops immutable immutability Asked in 27 Companies basic frequent | ||||
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| Very Frequently asked. Usually asked along with String Class related questions. | ||||
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| Ans. Class using which only immutable (objects that cannot be changed after initialization) objects can be created. | ||||
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| Discuss Correct / Improve java oops immutable immutability immutable immutability class string class basic interview question Asked in 18 Companies Basic frequent | ||||
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| Ans. We can make a class immutable by 1. Making all methods and variables as private. 2. Setting variables within constructor. Public Class ImmutableClass{ private int member; ImmutableClass(int var){ member=var; } } and then we can initialize the object of the class as ImmutableClass immutableObject = new ImmutableClass(5); Now all members being private , you cant change the state of the object. | ||||
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Which of the following is not an advantage of JSON over XML ?
