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Interview Questions and Answers - Order By Newest | ||||
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Ans. Simple Inner Class, Local Inner Class, Anonymous Inner Class, Static Nested Inner Class. | ||||
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Like Discuss Correct / Improve  java   inner classes   classes Asked in 6 Companies basic   frequent | ||||
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Frequently asked in Indian Service Companies. Tech Mahindra ( Based on 3 inputs ) and Infosys ( 3 inputs ) | ||||
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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. | ||||
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Like Discuss Correct / Improve  java   collections   list   set   map   list vs set vs map Asked in 8 Companies basic   frequent | ||||
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Frequently asked at HCL Technologies ( Based on 3 feedback ) | ||||
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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. | ||||
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Like Discuss Correct / Improve  java   exceptions   checked exceptions   unchecked exceptions   exception handling   checked vs unchecked exceptions Asked in 39 Companies basic   frequent | ||||
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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. | ||||
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Ans. Final variable is a variable constant that cannot be changed after initialization. | ||||
Sample Code for final variable | ||||
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Ans. Vectors are synchronized whereas Array lists are not. | ||||
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Ans. It in Java is used to indicate that a field should not be serialized. | ||||
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Like Discuss Correct / Improve  java   oops   serialization   transient   java keywords Asked in 39 Companies intermediate   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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Very frequently asked in phone and walk in interviews. | ||||
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Ans. An interface without any method declaration is called as marker interface. there are 3 in-built interfaces in JVM i.e. serializable, clonable, remote | ||||
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Very frequently asked. Usually difference between String,StringBuffer and StringBuilder is asked in different variations. | ||||
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Ans. StringBuffer is synchronized whereas StringBuilder is not. | ||||
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Ans. It is the process of examining / modifying the behaviour of an object at runtime. | ||||
Sample Code for reflection | ||||
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Ans. As we only downcast class in the hierarchy, The ClassCastException is thrown to indicate that code has attempted to cast an object to a subclass of which it is not an instance. | ||||
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Ans. A child object constructor always first needs to construct its parent. In Java it is done via an implicit call to the no-args constructor as the first statement | ||||
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Ans. Iterators in java are used to iterate over the Collection objects. Fail-Fast iterators immediately throw ConcurrentModificationException if there is any addition, removal or updation of any element. Fail-Safe iterators don't throw any exception if a collection is structurally modified while iterating over it. This is because, they operate on the clone of the collection and not on the original collection. | ||||
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Ans. Yes, but the overloaded main methods without single String[] argument doesn't get any special status by the JVM. They are just another methods that needs to be called explicitly. | ||||
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Like Discuss Correct / Improve  java   main method   overloading   yes-no Asked in 6 Companies intermediate   frequent | ||||
Very Frequently asked. | ||||
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Ans. throw is used to re throw an exception.throws is used to declare that the method throws the respective exceptions.try block is used to identify if the respective block has thrown any exception.catch is used to catch the exception that has been thrown by the respective try block. | ||||
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Ans. BlockingQueue is a Queue that supports operations that wait for the queue to become non-empty when retrieving and removing an element, and wait for space to become available in the queue when adding an element. | ||||
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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. | ||||
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Like Discuss Correct / Improve  get vs post   web service   rest Asked in 11 Companies basic   frequent | ||||
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Ans. Coupling is the degree of interdependence between software modules, a measure of how closely connected two modules are or the strength of the relationships between modules. Cohesion refers to the degree to which the elements of a module belong together. Cohesion measures the strength of relationship between pieces of functionality within a given module. | ||||
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Like Discuss Correct / Improve  coupling  cohesion Asked in 10 Companies   frequent | ||||
Frequently asked Generic Question. | ||||
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Ans. [Open Ended Answer] Usually answered stating your keen interest in the role offered and challenges and opportunities the role offers. | ||||
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Like Discuss Correct / Improve   Asked in 42 Companies   frequent | ||||
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This question was recently asked at 'Myntra,Compro Technologies'.This question is still unanswered. Can you please provide an answer. | ||||
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Like Discuss Correct / Improve   Asked in 2 Companies | ||||
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Ans. class A { void test() { System.out.println("test() method"); } } class B { void test() { System.out.println("test() method"); } } Suppose if Java allows multiple inheritance like this, class C extends A, B { } A and B test() methods are inheriting to C class. So which test() method C class will take? As A & B class test() methods are different , So here we would Facing Ambiguity. | ||||
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Like Discuss Correct / Improve  multiple inheritance  object oriented programming (oops)  oops concepts  diamond problem Asked in 20 Companies basic   frequent | ||||
Usually asked to entry level software developers. | ||||
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Ans. public static void main(String[] args) { int num1 = 1; int num2 = 2; num1 = num1^num2; num2 = num1^num2; num1 = num1^num2; System.out.print("num1 = " + num1 +", num2 = "+num2); } | ||||
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Ans. Prototype scope - A new object is created each time it is injected/looked up. It will use new SomeClass() each time. Singleton scope - It is the default scope. The same object is returned each time it is injected/looked up. Here it will instantiate one instance of SomeClass and then return it each time. | ||||
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Ans. Warm up time for certain technologies like Java ( JVM Warmup ) Performance Size of Deployable ( Bigger size packaging should go in S3 ) | ||||
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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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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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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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Ans. By static import , we can access the static members of a class directly without prefixing it with the class name. | ||||
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Ans. Collections class is a utility class having static methods for doing operations on objects of classes which implement the Collection interface. For example, Collections has methods for finding the max element in a Collection. | ||||
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Ans. Stands for Java API for XML Processing. This provides a common interface for creating and using SAX, DOM, and XSLT APIs in Java regardless of which vendor’s implementation is actually being used. | ||||
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Like Discuss Correct / Improve  java   java api   xml   xml processing   jaxp   abbreviation   technologies | ||||