JAVA Interview Questions

COREJAVA

·         Q1. What is the difference between an Abstract class and Interface?

·         Q2. What are checked and unchecked exceptions?

·         Q3. What is a user defined exception?

·         Q4. What is the difference between C++ & Java?

·         Q5. What are statements in JAVA ?

·         Q6. What is JAR file?

·         Q7. What is JNI?

·         Q8. What is serialization?

·         Q9. Why there are some null interface in java ? What does it mean ? Give me some null interfaces in JAVA?

·         Q10. Is synchronised a modifier?indentifier??what is it??

·         Q11. What is singleton class?where is it used?

·         Q12. What is a compilation unit?

·         Q13. Is string a wrapper class?

·         Q14.Why java does not have multiple inheritance?

·         Q15. Why java is not a 100% oops?

·         Q16. What is a resource bundle?

·         Q17. What is transient variable?

·         Q18. What is Collection API?

·         Q19. Is Iterator a Class or Interface? What is its use?

·         Q20. What is similarities/difference between an Abstract class and Interface?

·         Q21. What is a transient variable?

·         Q22. Which containers use a border Layout as their default layout?

·         Q23. Why do threads block on I/O?

·         Q24. How are Observer and Observable used?

·         Q25. What is synchronization and why is it important?

·         Q26. Can a lock be acquired on a class?

·         Q27. What's new with the stop(), suspend() and resume() methods in JDK 1.2?

·         Q28. Is null a keyword?

·         Q29. What is the preferred size of a component?

·         Q30. What method is used to specify a container's layout?

·         Q31. Which containers use a FlowLayout as their default layout?

·         Q32. What state does a thread enter when it terminates its processing?

·         Q33. What is the Collections API?

·         Q34. Which characters may be used as the second character of an identifier, but not as the first character of an identifier?.

·         Q35.What is the List interface?

·         Q36. How does Java handle integer overflows and underflows?

·         Q37.What is the Vector class?

·         Q38.What modifiers may be used with an inner class that is a member of an outer class?

·         Q39. What is an Iterator interface?

·         Q40. What is the difference between the >> and >>> operators?

·         Q41. Which method of the Component class is used to set the position and size of a component?

·         Q42. How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?

·         Q43. What is the difference between yielding and sleeping?

·         Q44. Which java.util classes and interfaces support event handling?

·         Q45. Is sizeof a keyword?

·         Q46. What are wrapped classes?

·         Q47. Does garbage collection guarantee that a program will not run out of memory?

·         Q48. What restrictions are placed on the location of a package statement within a source code file?

·         Q49. Can an object's finalize() method be invoked while it is reachable?

·         Q50. What is the immediate superclass of the Applet class?

·         Q51. What is the difference between preemptive scheduling and time slicing?

·         Q52. Name three Component subclasses that support painting.

·         Q53. What value does readLine() return when it has reached the end of a file?

·         Q54. What is the immediate superclass of the Dialog class?

·         Q55. What is clipping?

·         Q56. What is a native method?

·         Q57. Can a for statement loop indefinitely?

·         Q58. What are order of precedence and associativity, and how are they used?

·         Q59. When a thread blocks on I/O, what state does it enter?

·         Q60. To what value is a variable of the String type automatically initialized?

·         Q61. What is the catch or declare rule for method declarations?

·         Q62. What is the difference between a MenuItem and a CheckboxMenuItem?

·         Q63. What is a task's priority and how is it used in scheduling?

·         Q64. What class is the top of the AWT event hierarchy?

·         Q65. When a thread is created and started, what is its initialstate?

·         Q66. Can an anonymous class be declared as implementingan interface and extending a class?

·         Q67. What is the range of the short type?

·         Q68. What is the range of the char type?

·         Q69. In which package are most of the AWT events thatsupport the event-delegation model defined?

·         Q70. What is the immediate superclass of Menu?

·         Q71. What is the purpose of finalization?

·         Q72. Which class is the immediate superclass of theMenuComponent class.

·         Q73. What invokes a thread's run() method?

·         Q74. What is the difference between the Boolean & operatorand the && operator?

·         Q75. Name three subclasses of the Component class.

·         Q76. What is the GregorianCalendar class?

·         Q77. Which Container method is used to cause a containerto be laid out and redisplayed?

·         Q78. What is the purpose of the Runtime class?

·         Q79. How many times may an object's finalize() method beinvoked by the garbage collector?

·         Q80. What is the purpose of the finally clause of a try-catchfinally statement?

·         Q81. What is the argument type of a program's main()method?

·         Q82. Which Java operator is right associative?

·         Q83. What is the Locale class?

·         Q84. Can a double value be cast to a byte?

·         Q85. What is the difference between a break statement anda continue statement?

·         Q86. What must a class do to implement an interface?

·         Q87. What method is invoked to cause an object to beginexecuting as a separate thread?

·         Q88. Name two subclasses of the TextComponent class.

·         Q89. What is the advantage of the event-delegation modelover the earlier eventinheritance model?

·         Q90. Which containers may have a MenuBar?

·         Q91. How are commas used in the intialization and iterationparts of a for statement?

·         Q92. What is the purpose of the wait(), notify(), andnotifyAll() methods?

·         Q93. What is an abstract method?

·         Q94. How are Java source code files named?

·         Q95. What is the relationship between the Canvas class andthe Graphics class?

·         Q96.What are the high-level thread states?

·         Q97. What value does read() return when it has reached theend of a file?

·         Q98.Can a Byte object be cast to a double value?

·         Q99. What is the difference between a static and a nonstaticinner class?

·         Q100. What is the difference between the String andStringBuffer classes?

·         Q101. If a variable is declared as private, where may thevariable be accessed?

·         Q102. What is an object's lock and which object's havelocks?

·         Q103. What is the Dictionary class?

·         Q104. How are the elements of a BorderLayout organized?

·         Q105. How are the elements of a BorderLayout organized?

·         Q106. When can an object reference be cast to an interfacereference?

·         Q107. What is the difference between a Window and aFrame?

·         Q108. Which class is extended by all other classes?

·         Q109. Can an object be garbage collected while it is stillreachable?

·         Q110. Is the ternary operator written x : y ? z or x ? y : z ?

·         Q111. What is the difference between the Font andFontMetrics classes?

·         Q112. How is rounding performed under integer division?

·         Q113.What happens when a thread cannot acquire a lockon an object?

·         Q114. What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream classhierarchy?

·         Q115. What classes of exceptions may be caught by a catchclause?

·         Q116. If a class is declared without any access modifiers,where may the class be accessed?

·         Q117. What is the SimpleTimeZone class?

·         Q118. What is the Map interface?

·         Q119. Does a class inherit the constructors of itssuperclass?

·         Q120. For which statements does it make sense to use alabel?

·         Q121. What is the purpose of the System class?

·         Q122.Which TextComponent method is used to set aTextComponent to the read-only state?

·         Q123. How are the elements of a CardLayout organized?

·         Q124. Is &&= a valid Java operator?

·         Q125. Name the eight primitive Java types?

·         Q126. Which class should you use to obtain designinformation about an object?

·         Q127. What is the relationship between clipping andrepainting?

·         Q128. Is "abc" a primitive value?

·         Q129. What is the relationship between an event-listenerinterface and an event-adapter class?

·         Q130. What restrictions are placed on the values of eachcase of a switch statement?

·         Q131. What modifiers may be used with an interfacedeclaration?

·         Q132. Is a class a subclass of itself?

·         Q133. What is the highest-level event class of the eventdelegationmodel?

·         Q134. What event results from the clicking of a button?

·         Q135. How can a GUI component handle its own events?

·         Q136. What is the difference between a while statementand a do statement?

·         Q137. How are the elements of a GridBagLayout organized?

·         Q138. What advantage do Java's layout managers provideover traditional windowing systems?

·         Q139. What is the Collection interface?

·         Q140. What modifiers can be used with a local inner class?

·         Q141.What is the difference between static and non-staticvariables?

·         Q142. What is the difference between the paint() andrepaint() methods?

·         Q143. What is the purpose of the File class?

·         Q144. Can an exception be rethrown?

·         Q145. Which Math method is used to calculate the absolutevalue of a number?

·         Q146. How does multithreading take place on a computerwith a single CPU?

·         Q147. When does the compiler supply a default constructorfor a class?

·         Q148. When is the finally clause of a try-catch-finallystatement executed?

·         Q149. Which class is the immediate superclass of theContainer class?

·         Q150. If a method is declared as protected, where may themethod be accessed?

·         Q151. How can the Checkbox class be used to create a radiobutton?

·         Q152. Which non-Unicode letter characters may be used asthe first character of an identifier?

·         Q153. What restrictions are placed on method overloading?

·         Q154. What happens when you invoke a thread's interruptmethod while it is sleeping or waiting?

·         Q155. What is casting?

·         Q156. What is the return type of a program's main()method?

·         Q157. Name four Container classes.

·         Q158. What is the difference between a Choice and a List?

·         Q159. What class of exceptions are generated by the Javarun-time system?

·         Q160. What class allows you to read objects directly from astream?

·         Q161. What is the difference between a field variable and alocal variable?

·         Q162. Under what conditions is an object's finalize()method invoked by the garbage collector?

·         Q163. How are this() and super() used with constructors?

·         Q164. What is the relationship between a method's throws clause and the exceptions that can be thrown during the method's execution??

·         Q165. What is the difference between the JDK 1.02 event model and the event-delegation model introduced withJDK 1.1?

·         Q166. How is it possible for two String objects withidentical values not to be equal under the == operator?

·         Q167. Why are the methods of the Math class static?

·         Q168. What Checkbox method allows you to tell if aCheckbox is checked?

·         Q169. What state is a thread in when it is executing?

·         Q170. What are the legal operands of the instanceofoperator?

·         Q171. How are the elements of a GridLayout organized?

·         Q172.What an I/O filter?

·         Q173.If an object is garbage collected, can it becomereachable again?

·         Q174. What is the Set interface?

·         Q175. What classes of exceptions may be thrown by a throwstatement?

·         Q176. What are E and PI?

·         Q177.Are true and false keywords?

·         Q178.What is a void return type?

·         Q179. What is the purpose of the enableEvents() method?

·         Q180. What is the difference between the File andRandomAccessFile classes?

·         Q181. What happens when you add a double value to aString?

·         Q182.What is your platform's default character encoding?

·         Q183. Which package is always imported by default?

·         Q184. What interface must an object implement before itcan be written to a stream as an object?

·         Q185. How are this and super used?

·         Q186.What is the purpose of garbage collection?

·         Q187. What is a compilation unit?

·         Q188. What interface is extended by AWT event listeners?

·         Q189. What restrictions are placed on method overriding?

·         Q190. How can a dead thread be restarted?

·         Q191. What happens if an exception is not caught?

·         Q192. What is a layout manager?

·         Q193. Which arithmetic operations can result in thethrowing of an ArithmeticException?

·         Q194. What are three ways in which a thread can enter thewaiting state?

·         Q195. Can an abstract class be final?

·         Q196. What is the ResourceBundle class?

·         Q197. What happens if a try-catch-finally statement does not have a catch clause to handle an exception that is thrown within the body of the try statement?

·         Q198. What is numeric promotion?

·         Q199. What is the difference between a Scrollbar and aScrollPane?

·         Q200. What is the difference between a public and a nonpublicclass?

·         Q201. To what value is a variable of the boolean typeautomatically initialized?

·         Q202.Can try statements be nested?

·         Q203.What is the difference between the prefix and postfixforms of the ++ operator?

·         Q204. What is the purpose of a statement block?

·         Q205. What is a Java package and how is it used?

·         Q206. What modifiers may be used with a top-level class?

·         Q207.What are the Object and Class classes used for?

·         Q208. How does a try statement determine which catchclause should be used to handle an exception?

·         Q209. Can an unreachable object become reachable again?

·         Q210. When is an object subject to garbage collection?

·         Q211. What method must be implemented by all threads?

·         Q212.What methods are used to get and set the text labeldisplayed by a Button object?

·         Q213. Which Component subclass is used for drawing andpainting?

·         Q214. What are synchronized methods and synchronizedstatements?

·         Q215. What are the two basic ways in which classes thatcan be run as threads may be defined?

·         Q216. What are the problems faced by Java programmerswho don't use layout managers?

·         Q217. What is the difference between an if statement and aswitch statement?

·         Q218. What happens when you add a double value to aString?

·         Q219. What is the List interface?