Rarely asked Interview Questions and Answers

Interview Questions and Answers - Order By Newest

Q41. What is Closeable ?

Core Java

Ans. A Closeable is an interface which is a source or destination of data that can be closed.

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Q42. Name few Locale classes and interfaces ?

Ans. http://www.buggybread.com/2015/01/java-locale-classes-and-interfaces.html

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Rarely asked as it was introduced with Java 8.

Q43. Which keyword specify that a variable is effectively final ? a. final b. No Keyword c. Both of the above d. None of the above

Core Java

Ans. No Keyword

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Q44. What is RI or Reference Implementation ?

Ans. RI or Reference Implementation is a sample implementation provided for the API's / Specs, usually by their developers. This is usually a part of API documentation.

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Q45. What is GregorianCalendar class ?

Ans. This class provides support for traditional Western calendars.

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Q46. What is "Instance Initializer block" ?

Ans. Instance Initializer block is used to initialize the instance data member. It run each time when object of the class is created.

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Q47. Is it Necessary to send a POST request with the Payload or a body ?

Web Service

Ans. No, we can also send an empty body with the POST Request.

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Q48. Can I hit the Rest Post Request through a browser address bar if it's not expecting any payload / body ?

Rest

Ans. No, even if there is no payload, you can't hit the POST request by typing it into browser address bar. You will need a client that can make a POST Request.

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Q49. What happens to the Exception object after the exception handling is done ?

Core Java

Ans. As with all other objects its garbage collected after its usage unless its rethrown.

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Usually asked with Questions related to Generics.

Q50. What are Type Erasures in Java ?

Core Java

Ans. Type erasure applies to the use of generics. When generics are used, they're pre compiled into compile time checks and execution-time casts.

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Q51. How can one determine if JVM is 32-bit or 64-bit from Java Program ?

Core Java

Ans. There is a Java system property "sun.arch.data.model" that can tell if JVM is 32 bit of 64 bit

System.getProperty("sun.arch.data.model") can be used to get that property.

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Q52. Is ++ or -- operation thread safe in Java ?

Core Java

Ans. No

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Q53. How can we find the memory usage of JVM from Java code?

Core Java

Ans. Using Runtime object.

Runtime runtime = Runtime.getRuntime();

runtime.totalMemory();
runtime.freeMemory();

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Q54. How can we catch an exception thrown by another thread ?

Core Java

Ans. http://stackoverflow.com/a/6548203/2789764

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Q55. What is serialVersionUID ?

Core Java

Ans. Everytime an object is serialized the java serialization mechanism automatically computes a hash value by passing the meta information for the class. This id is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization

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Q56. Is there a way to know size of an object in Java ?

Core Java

Ans. No, Java doesn't have a sizeOf operator. In C / C++ , its required to determine how much memory allocation is required which is not the case with Java. Java handles memory allocation and deallocation intrinsically.

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Q57. How does Java handle integer overflows and underflows?

Core Java

Ans. It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.

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Q58. Which memory segment holds String Pool in Java ?

Core Java

Ans. String Pool resides in runtime constant Pool which is a part of Heap memory segment.

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Q59. What is the difference between

File f = new File("homexyz.txt");

and

File f = File.createTempFile("xyz",".txt","home"); ?

Core Java

Ans. First will not create physical file in storage whereas the second will.

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Q60. What is Exception Wrapping ?

Ans. Exception wrapping is wrapping an exception object within another exception object and then throwing the outer exception.

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Q61. Why can we have a static inner class but not a static Top level class in Java ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

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Q62. How ConcurrentHashMap provides better performance compared to HashTable ?

Core Java

Ans. ConcurrentHashMap uses multiple buckets to store Data and hence avoid read locks which facilitates better performance.

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Q63. What is an applet ?

Java EE

^{This question was recently asked at 'American International Group (AIG)'.This question is still unanswered. Can you please provide an answer.}

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Q64. What is a weak reference ?

Core Java

Ans. A weak reference is a reference that gets removed on the next garbage collection cycle.

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Q65. What value you would like to see in an employee if you own a company ?

General

Ans. The intent of this question is to see what values as a employee you have. So answer this cautiously as they will try to judge you on the basis of this answer.

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Q66. How Bitly shortens the URL ?

Web

^{This question was recently asked at 'Symantec'.This question is still unanswered. Can you please provide an answer.}

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Q67. What is the difference between TreeSet and TreeMap ?

Core Java

Ans. TreeSet contains only values as elements whereas TreeMap contains Key value pairs.

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Q68. What is MVC in GUI components ?

Design

Ans. The Model/View/Controller pattern, a strategy for dividing responsibility in a GUI component.

The model is the data for the component.

The view is the visual presentation of the component on the screen.

The controller is responsible for reacting to events by changing the model.

According to the MVC pattern, these responsibilities should be handled by different objects.

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Q69. How is the virtual method table implemented in Java?

Core Java

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Q70. How many VTables are there for each class ?

Core Java

Ans. There is one VTable for each class.

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