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| Interview Questions and Answers for 'Trimax IT Infrastructure' - 10 question(s) found - Order By Rating | ||||
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| Ans. OOPs or Object Oriented Programming is a Programming model which is organized around Objects instead of processes. Instead of a process calling series of processes, this model stresses on communication between objects. Objects that all self sustained, provide security by encapsulating it's members and providing abstracted interfaces over the functions it performs. OOP's facilitate the following features 1. Inheritance for Code Reuse 2. Abstraction for modularity, maintenance and agility 3. Encapsulation for security and protection 4. Polymorphism for flexibility and interfacing | ||||
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 Discuss Correct / Improve  oops oops features  Asked in 260 Companies  basic  frequent | ||||
 Usually asked in relation to casting and ClassCastException. | ||||
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| Ans. The operator instanceOf is used to verify if the specified object is the instance of specified class or interface. Syntax if(x instanceOf ABC) where x is an object reference and ABC could be a class name or interface name. The above statement will be true if x holds an object that is an instance of ABC or any of the child class of ABC or if x holds an object that implements ABC. instanceOf operator is used to verify in case of downcasting. For ex - DerivedClass extends BaseClass x is the reference of BaseClass but holds DerivedClass object ( Polymorphism ) There is an operation that is defined in Derived Class, let's say derivedClassMethod() We cannot call derivedClassMethod() directly using x as x is reference of BaseClass and not DerivedClass and hence can only access methods that are defined in BaseClass and overridden in derived class. Though we can cast it to DerivedClass as following ((DerivedClass)x).derivedClassMethod(); But it may throw ClassCastException in case x doesn't hold an instance of DerivedClass at that point. So before casting it to DerivedClass we may like to make sure that it is an instance of DerivedClass and hence won't throw ClassCastException. So we make a check for it if(x instanceOf DerivedClass) { ((DerivedClass)x).derivedClassMethod(); } | ||||
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| Discuss Correct / Improve instanceOf instanceOf operator Why we need instanceOf operator use of instanceOf operator Asked in 2 Companies Intermediate frequent | ||||
| Very frequently asked. Usually among very first few questions. | ||||
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| Ans. Encapsulation is a feature of OOP's that binds the data and it's associated methods together as a single unit and facilitate protection and data hiding by providing minimal interface to outside. For example - member variables are declared private and are accessed through public methods. Moreover we have private methods that can only be used internally and hence providing minimal interface to outside class through use of public methods. | ||||
 Sample Code for encapsulation | ||||
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| Discuss Correct / Improve encapsulation object oriented programming (oops) oops concepts oops oops concepts oops features Asked in 4 Companies Basic frequent | ||||
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| Ans. final keyword is a modifier that means differently when applied to variables, methods and classes. 1. Final variable cannot be changed once initialized 2. Final method cannot be overridden 3. Final class cannot be sub classed | ||||
| Sample Code for final variable Sample Code for final method Sample Code for final class | ||||
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| Discuss Correct / Improve final final keyword Asked in 1 Companies Basic frequent | ||||
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| Ans. JVM (Java Virtual Machine) is an abstract machine. It is a specification that provides runtime environment in which java bytecode can be executed.JVMs are available for many hardware and software platforms (i.e. JVM is platform dependent).Runtime Instance Whenever you write java command on the command prompt to run the java class, an instance of JVM is createdThe JVM performs following operation:Loads codeVerifies codeExecutes codeProvides runtime environment | ||||
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| Discuss Correct / Improve memory management jvm Asked in 3 Companies basic frequent | ||||
| Basic and Very Frequently asked. | ||||
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| Ans. Polymorphism means the condition of occurring in several different forms. Polymorphism in Java is achieved in two manners 1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas 2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding. | ||||
| Sample Code for overloading Sample Code for overriding | ||||
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| Discuss Correct / Improve polymorphism object oriented programming (oops) oops concepts oops concepts Asked in 108 Companies Basic frequent | ||||
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| Frequently asked in Infosys India | ||||
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| Ans. String pool (String intern pool) is a special storage area in Java heap. When a string is created and if the string already exists in the pool, the reference of the existing string will be returned, instead of creating a new object and returning its reference. | ||||
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| Discuss Correct / Improve java oops string string class string pool heap memory Asked in 31 Companies intermediate frequent | ||||
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| Ans. Within message.properties file. | ||||
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| Discuss Correct / Improve j2ee web application struts spring Asked in 1 Companies | ||||
| Frequently asked in CTS ( Based on 2 feedback ) | ||||
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| Ans. Comparable interface is used for single sequence sorting i.e.sorting the objects based on single data member where as comparator interface is used to sort the object based on multiple data members. | ||||
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| Discuss Correct / Improve java java.util comparable comparator collections Asked in 23 Companies basic frequent | ||||
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| Ans. private static boolean isPalindrome(String str) { if (str == null) return false; StringBuilder strBuilder = new StringBuilder(str); strBuilder.reverse(); return strBuilder.toString().equals(str); } | ||||
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| Discuss Correct / Improve java string stringbuilder stringbuilder string class code palindrome Asked in 38 Companies Basic frequent | ||||
Static Polymorphic in Java is achieved through .. 
