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	Core Java FAQs 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?