More than 3000 questions in repository. There are more than 900 unanswered questions. Click here and help us by providing the answer. Have a video suggestion. Click Correct / Improve and please let us know.
Ans. <a href="http://www.programcreek.com/2009/02/diagram-for-hierarchy-of-exception-classes/" rel="nofollow">http://www.programcreek.com/2009/02/diagram-for-hierarchy-of-exception-classes/</a>
Help us improve. Please let us know the company, where you were asked this question :
Ans. 1. Switching Overheads - Even though multi threading aims at improving performance by reducing the wait time and hence improving overall throughput, there is a cost of switching resources between threads and sometime this cost can surpass the benefits if there isnt much wait for IO or external communication.
2. Debugging is hard with multi threaded code.
3. Deadlock - Execution of multi threaded code many a times lead to deadlock due to shared resources.
Help us improve. Please let us know the company, where you were asked this question :
Ans. GET is supposed to get information from the server. Client sends the minimal information so that Server can respond with the response body on basis of request. For example - You want to get complete employment record for employee id 123
POST is supposed to send the information for submission. Payload or a Body is usually sent so that it can be persisted on the server. For example - Sending the complete information of an employee ( id, name , dept etc ) to the server for persisting it.
Help us improve. Please let us know the company, where you were asked this question :
Ans. When a Table Join itself , it's a Self Join. For example - we like to know the pair of department names where first dept has lesser employees than the later.
Select D1.name , D2.name from Dept D1, Dept D2 where D1.employee_count < D2.employee_count
Help us improve. Please let us know the company, where you were asked this question :
Ans. JRE or Java Runtime Environment is the Java Virtual Machine on which class files are executed. It includes borwser plugins that facilitates execution of class files in browsers.
JDK or Java Development Kit includes JRE , compiler and development tools.
Help us improve. Please let us know the company, where you were asked this question :
Ans. Deployment Descriptor which is usually web.xml is used to specify the classes, resources and configuration of the application and how the web server uses them to serve web requests.This file is usually added to WEB-INF folder and contains following
* Servlet entries and url mapping
* Plugins
* Some info regarding authentication / filters
* Landing Page
* Event Handlers
Help us improve. Please let us know the company, where you were asked this question :
Ans. Car Engine is an example of encapsulation and abstraction. You ignite the car using an interface called starter and least bothered about how the tire actually moves (This is abstraction). The engine encapsulates the complete process to itself only and doesn't allow you to start the other components like the radiator etc ( this is excapsulation )
Help us improve. Please let us know the company, where you were asked this question :
Ans. They are different the way their elements are stored in memory. TreeMap stores the Keys in order whereas HashMap stores the key value pairs randomly.
Ans. List - Members are stored in sequence in memory and can be accessed through index.
Set - There is no relevance of sequence and index. Sets doesn't contain duplicates whereas multiset can have duplicates.
Map - Contains Key , Value pairs.
Help us improve. Please let us know the company, where you were asked this question :
Ans. Checked exceptions are the exceptions for which compiler throws an errors if they are not checked whereas unchecked exceptions are caught during run time only and hence can't be checked.
Help us improve. Please let us know the company, where you were asked this question :
Ans. Its a method which cannot be overridden. Compiler throws an error if we try to override a method which has been declared final in the parent class.
Help us improve. Please let us know the company, where you were asked this question :
Ans. 1. Multithreading provides better interaction with the user by distribution of task
2. Threads in Java appear to run concurrently, so it provides simulation for simultaneous activities.The processor runs each thread for a short time and switches among the threads to simulate sim-ultaneous execution (context-switching) and it make appears that each thread has its own processor.By using this feature, users can make it appear as if multiple tasks are occurring simultaneously when, in fact, each is running for only a brief time before the context is switched to the next thread.
3. We can do other things while waiting for slow I/O operations.In the java.iopackage, the class InputStreamhas a method, read(), that blocks until a byte is read from the stream or until an IOExceptionis thrown. The thread that executes this method cannot do anything elsewhile awaiting the arrival of another byte on the stream.
Help us improve. Please let us know the company, where you were asked this question :
Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc. The value received from hashcode() is used as bucket number for storing elements. This bucket number is the address of the element inside the set/map. when you do contains() then it will take the hashcode of the element, then look for the bucket where hashcode points to and if more than 1 element is found in the same bucket (multiple objects can have the same hashcode) then it uses the equals() method to evaluate if object are equal, and then decide if contain() is true or false, or decide if element could be added in the set or not.
Help us improve. Please let us know the company, where you were asked this question :
Ans. 1. String Pool - When a string is created and if it exists in the pool, the reference of the existing string will be returned instead of creating a new object. If string is not immutable, changing the string with one reference will lead to the wrong value for the other references.
Example -
String str1 = "String1";
String str2 = "String1"; // It doesn't create a new String and rather reuses the string literal from pool
// Now both str1 and str2 pointing to same string object in pool, changing str1 will change it for str2 too
2. To Cache its Hashcode - If string is not immutable, One can change its hashcode and hence it's not fit to be cached.
3. Security - String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment.
Help us improve. Please let us know the company, where you were asked this question :
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.
Help us improve. Please let us know the company, where you were asked this question :
More than 3000 questions in repository.
Discuss 
exception hierarchy exceptions 
Asked in 3 Companies
basic 
frequent
Frequently asked to Fresh graduates.
Try 1 Question(s) Test
Sample Code for treemap
Binary Search requires that the collection should be
