Top 100 Java Questions

Posted by Stephen thangaraj at 18:23

1. What is the diffrence between an Abstract class and Interface ?
2. What is user defined exception ?
3. What do you know about the garbate collector ?
4. What is the difference between C++ & Java ?
5. Explain RMI Architecture?
6. How do you communicate in between Applets & Servlets ?
7. What is the use of Servlets ?
8. What is JDBC? How do you connect to the Database ?
9. In an HTML form I have a Button which makes us to open another page in 15 seconds. How will do you that ?
10. What is the difference between Process and Threads ?
11. What is the difference between RMI & Corba ?
12. What are the services in RMI ?
13. How will you initialize an Applet ?
14. What is the order of method invocation in an Applet ?
15. When is update method called ?
16. How will you pass values from HTML page to the Servlet ?
17. Have you ever used HashTable and Dictionary ?
18. How will you communicate between two Applets ?
19. What are statements in JAVA ?
20. What is JAR file ?
21. What is JNI ?
22. What is the base class for all swing components ?
23. What is JFC ?
24. What is Difference between AWT and Swing ?
25. Considering notepad/IE or any other thing as process, What > will happen if you start notepad or IE 3 times? Where 3 processes are started or 3 threads are started ?
26. How does thread synchronization occurs inside a monitor ?
27. How will you call an Applet using a Java Script function ?
28. Is there any tag in HTML to upload and download files ?
29. Why do you Canvas ?
30. How can you push data from an Applet to Servlet ?
31. What are 4 drivers available in JDBC ?
32. How you can know about drivers and database information ?
33. If you are truncated using JDBC, How can you know ..that how much > > > data is truncated ?
34. And What situation , each of the 4 drivers used ?
35. How will you perform transaction using JDBC ?
36. In RMI, server object first loaded into the memory and then the stub reference is sent to the client ? or whether a stub reference is directly sent to the client ?
37. Suppose server object is not loaded into the memory, and theclient request for it , what will happen?
38. What is serialization ?
39. Can you load the server object dynamically? If so, what are the major 3 steps involved in it ?
40. What is difference RMI registry and OSAgent ?
41. To a server method, the client wants to send a value 20, with this value exceeds to 20,. a message
should be sent to the client ? What will you do for achieving for this ?
42. What are the benefits of Swing over AWT ?
43. Where the CardLayout is used ?
44. What is the Layout for ToolBar ?
45. What is the difference between Grid and GridbagLayout ?
46. How will you add panel to a Frame ?
47. What is the corresponding Layout for Card in Swing ?
48. What is light weight component ?
49. Can you run the product development on all operating systems ?
50. What is the webserver used for running the Servlets ?
51. What is Servlet API used for conneting database ?
52. What is bean ? Where it can be used ?
53. What is difference in between Java Class and Bean ?
54. Can we send object using Sockets ?
55. What is the RMI and Socket ?
56. How to communicate 2 threads each other ?
57. What are the files generated after using IDL to Java Compilet ?
58. What is the protocol used by server and client ?
59. Can I modify an object in CORBA ?
60. What is the functionality stubs and skeletons ?
61. What is the mapping mechanism used by Java to identify IDL language ?
62. Diff between Application and Applet ?
63. What is serializable Interface ?
64. What is the difference between CGI and Servlet ?
65. What is the use of Interface ?
66. Why Java is not fully objective oriented ?
67. Why does not support multiple Inheritance ?
68. What it the root class for all Java classes ?
69. What is polymorphism ?
70. Suppose If we have variable ' I ' in run method, If I can create one or more thread each thread will
occupy a separate copy or same variable will be shared ?
71. In servlets, we are having a web page that is invoking servlets username and password ? which is cheks in the database ? Suppose the second page also If we want to verify the same information whether it will connect to the database or it will be used previous information?
72. What are virtual functions ?
73. Write down how will you create a binary Tree ?
74. What are the traverses in Binary Tree ?
75. Write a program for recursive Traverse ?
76. What are session variable in Servlets ?
77. What is client server computing ?
78. What is Constructor and Virtual function? Can we call Virtual funciton in a constructor ?
79. Why we use OOPS concepts? What is its advantage ?
80. What is the middleware ? What is the functionality of Webserver ?
81. Why Java is not 100 % pure OOPS ? ( EcomServer )
82. When we will use an Interface and Abstract class ?
83. What is an RMI?
84. How will you pass parameters in RMI ? Why u serialize?
85. What is the exact difference in between Unicast and Multicast object ? Where we will use ?
86. What is the main functionality of the Remote Reference Layer ?
87. How do you download stubs from a Remote place ?
88. What is the difference in between C++ and Java ? can u explain in detail ?
89. I want to store more than 10 objects in a remote server ? Which methodology will follow ?
90. What is the main functionality of the Prepared Statement ?
91. What is meant by static query and dynamic query ?
92. What are the Normalization Rules ? Define the Normalization ?
93. What is meant by Servelet? What are the parameters of the service method ?
94. What is meant by Session ? Tell me something about HTTPSession Class ?
95. How do you invoke a Servelt? What is the difference in between doPost and doGet methods ?
96. What is the difference in between the HTTPServlet and Generic Servlet ? Expalin their methods ? Tell me their parameter names also ?
97. Have you used threads in Servelet ?
98. Write a program on RMI and JDBC using StoredProcedure ?
99. How do you sing an Applet ?
100. In a Container there are 5 components. I want to display the all the components names, how will you do that one ?
101. Why there are some null interface in java ? What does it mean ? Give me some null interfaces in
102. Tell me the latest versions in JAVA related areas ?
103. What is meant by class loader ? How many types are there? When will we use them ?
104. How do you load an Image in a Servlet ?
105. What is meant by flickering ?
106. What is meant by distributed Application ? Why we are using that in our applications ?
107. What is the functionality of the stub ?
108. Have you used any version control ?
109. What is the latest version of JDBC ? What are the new features are added in that ?
110. Explain 2 tier and 3 -tier Architecture ?
111. What is the role of the webserver ?
112. How have you done validation of the fileds in your project ?
113. What is the main difficulties that you are faced in your project ?
114. What is meant by cookies ? Explain ?
Make sure you have a copy of your resume in front of you. OK to have a cheat sheet or two - just don't let anyone hear papers shuffling.
Know your OOA&D definitions, such as polymorphism, inheritance, etc.
Know the difference between an interface and an abstract class.
Know that Java does not support multiple inheritance the way C++ does.
Know that you implement an interface (can implement more than one).
Know that you extend an abstract class (can only extend more than one).
Know about the access modifiers: public/friendly(default)/protected/private. Be able to explain in one or two sentences for each case. This is where you can get tangled up in a phone conversation and confuse the check out of the interviewer and yourself.
Know AWT Event Model - tough to do over the phone - but you may get hit on a question.
Know the two ways to start a thread - "extending Thread" or "implementing Runnable".
Know that the method is "run" but to run a thread you use "start".

 How can I improve the performance of a java application, what are the java optimization
That question is about as meaningful as "how do you code stuff?" There's no one right answer, and the
interviewer probably just wanted to see if you knew *anything* about optimization. The answer is to go to the Performance thread and read the postings. If you search there for "books", you should find some good references which will get you started. You should also search for "tools".

2. What should you do to ensure that your applet works exactly the same way on both IE and netscape.
Short answers include: make sure they use the same JVM, don't use complex GUIs, and most importantly test to be certain! Personally, I'd question the benefit of the applet and ask if could be done with JSPs.

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