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| Core java - Interview Questions and Answers for 'Wits' - 12 question(s) found - Order By Newest | ||||
 Very frequently asked. Among first few questions in almost all interviews. Among Top 5 frequently asked questions. Frequently asked in Indian service companies (HCL,TCS,Infosys,Capgemini etc based on multiple feedback ) and Epam Systems | ||||
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| Ans. "equals" is the method of object class which is supposed to be overridden to check object equality, whereas "==" operator evaluate to see if the object handlers on the left and right are pointing to the same object in memory. x.equals(y) means the references x and y are holding objects that are equal. x==y means that the references x and y have same object. Sample code: String x = new String("str"); String y = new String("str"); System.out.println(x == y); // prints false System.out.println(x.equals(y)); // prints true | ||||
 Sample Code for equals | ||||
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 Discuss Correct / Improve  java string comparison string object class == equals object equality operator == vs equals equals vs ==  Asked in 294 Companies  basic  frequent | ||||
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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 | ||||
| Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. Frequently asked in HCL Technologies, TCS and Accenture. | ||||
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| Ans. final - constant variable, objects cannot be de-referenced, restricting method overriding, restricting class sub classing. finally - handles exception. The finally block is optional and provides a mechanism to clean up regardless of what happens within the try block. Use the finally block to close files or to release other system resources like database connections, statements etc. finalize() - method helps in garbage collection. A method that is invoked before an object is discarded by the garbage collector, allowing it to clean up its state. | ||||
| Sample Code for final Sample Code for finally Sample Code for finalize | ||||
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| Discuss Correct / Improve java oops final finally finalize final vs finally vs finalize Asked in 61 Companies basic frequent | ||||
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| 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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| Ans. Yes, That is possible class A { public static void main(String args[]){ if(System.out.printf("Hello World")==null){} } } | ||||
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| Discuss Correct / Improve Hello World Hello world without ; Asked in 2 Companies rare | ||||
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| Ans. Yes, doesn't provide exclusive access as we cannot allocate and deallocate memory exclusively as Java internally manages it. The advantage of this is that it relieves the coder for such tasks and helps protect from many bugs that may get introduced with imperfect coding. Moreover as java garbage collector collects all unclaimed memory or objects, it helps the application from memory leaks. On the flip side , as coder doesn't have extensive excess to memory , it is upto java to decide on the state for programming construct and data storage and hence may introduce some security risks. For example - Java keeps string literals in string pool and there is no exclusive way to remove it and hence may stay and sensitive data in string pool may introduce security issues. Moreover when we overwrite a value or object for a variable / reference, it is upto java to purge those values and hence it may stay in memory for a while till java decide that it is no longer referenced and hence should be removed and hence makes it vulnerable for inappropriate access. | ||||
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| Discuss Correct / Improve disadvantages of garbage collection advantages and disadvantages of java memory management java for security applications java with sensitive data memory management | ||||
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| Ans. Variables used in a switch statement can only be a byte, short, int, or char ( and String with Java 7 and above ) | ||||
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| Discuss Correct / Improve java switch variable data type basic rare | ||||
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| Ans. Java 7 | ||||
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| Discuss Correct / Improve java switch string in switch | ||||
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| Ans. http://stackoverflow.com/questions/18799591/print-natural-sequence-with-help-of-2-threads1-is-printing-even-and-2nd-is-pri | ||||
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| Discuss Correct / Improve print natural numbers with two threads multithreading multi threading threads code coding makemytrip.com | ||||
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| Ans. if statement is used to do 2 direction branching whereas switch is used to do multi direction branching in Java. Yes we can replace all switch statements with nested if statements. | ||||
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| Discuss Correct / Improve switch if vs switch | ||||
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| Ans. Yes | ||||
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| Discuss Correct / Improve enum enum within enum | ||||
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| Ans. Context Switching is the process of storing and restoring of CPU state so that Thread execution can be resumed from the same point at a later point of time. | ||||
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| Discuss Correct / Improve Threads multithreading context switching | ||||
Which of the following statement is not true ?
