Java Interview Guide : 200+ Interview Questions and Answers

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How about Quickly Revising all the Important Java Concepts in about 6 Hours before an interview?

Preparing for Java Interview is tricky. You would need to get a good understanding of new features and revise concepts you used in your preparation. This course helps you Prepare for Java Interview with hands-on code examples covering 200+ Java Interview Questions and Answers on varied range of topics listed below. 

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******* Questions Discussed in this Interview Course *******

Java Platform

1 . Why is Java so popular?

2 . What is platform independence?

3 . What is bytecode?

4 . Compare JDK vs JVM vs JRE 

5 . What are the important differences between C++ and Java?

6 . What is the role for a classloader in Java?

Wrapper Classes

7 . What are Wrapper classes?

8 . Why do we need Wrapper classes in Java?

9 . What are the different ways of creating Wrapper class instances?

10 . What are differences in the two ways of creating Wrapper classes?

11 . What is auto boxing?

12 . What are the advantages of auto boxing?

13 . What is casting?

14 . What is implicit casting?

15 . What is explicit casting?

Strings

16 . Are all String’s immutable?

17 . Where are String values stored in memory?

18 . Why should you be careful about String concatenation(+) operator in loops?

19 . How do you solve above problem?

20 . What are differences between String and StringBuffer?

21 . What are differences between StringBuilder and StringBuffer?

22 . Can you give examples of different utility methods in String class?

Object oriented programming basics

23 . What is a class?

24 . What is an object?

25 . What is state of an object?

26 . What is behavior of an object?

27 . What is the super class of every class in Java?

28 . Explain about toString method ?

29 . What is the use of equals method in Java?

30 . What are the important things to consider when implementing equals method?

31 . What is the Hashcode method used for in Java?

32 . Explain inheritance with examples . 

33 . What is method overloading?

34 . What is method overriding?

35 . Can super class reference variable can hold an object of sub class?

36 . Is multiple inheritance allowed in Java?

37 . What is an interface?

38 . How do you define an interface?

39 . How do you implement an interface?

40 . Can you explain a few tricky things about interfaces?

41 . Can you extend an interface?

42 . Can a class extend multiple interfaces?

43 . What is an abstract class?

44 . When do you use an abstract class?

45 . How do you define an abstract method?

46 . Compare abstract class vs interface?

47 . What is a constructor?

48 . What is a default constructor?

49 . Will this code compile?

50 . How do you call a super class constructor from a constructor?

51 . Will this code compile?

52 . What is the use of this()?

53 . Can a constructor be called directly from a method?

54 . Is a super class constructor called even when there is no explicit call from a sub class constructor?

Advanced object oriented concepts

55 . What is polymorphism?

56 . What is the use of instanceof operator in Java?

57 . What is coupling?

58 . What is cohesion?

59 . What is encapsulation?

60 . What is an inner class?

61 . What is a static inner class?

62 . Can you create an inner class inside a method?

63 . What is an anonymous class?

Modifiers

64 . What is default class modifier?

65 . What is private access modifier?

66 . What is default or package access modifier?

67 . What is protected access modifier?

68 . What is public access modifier?

69 . What access types of variables can be accessed from a class in same package?

70 . What access types of variables can be accessed from a class in different package?

71 . What access types of variables can be accessed from a sub class in same package?

72 . What access types of variables can be accessed from a sub class in different package?

73 . What is the use of a final modifier on a class?

74 . What is the use of a final modifier on a method?

75 . What is a final variable?

76 . What is a final argument?

77 . What happens when a variable is marked as volatile?

78 . What is a static variable?

conditions & loops

79 . Why should you always use blocks around if statement?

80 . Guess the output

81 . Guess the output

82 . Guess the output of this switch block . 

83 . Guess the output of this switch block?

84 . Should default be the last case in a switch statement?

85 . Can a switch statement be used around a String

86 . Guess the output of this for loop

87 . What is an enhanced for loop?

88 . What is the output of the for loop below?

89 . What is the output of the program below?

90 . What is the output of the program below?

Exception handling

91 . Why is exception handling important?

92 . What design pattern is used to implement exception handling features in most languages?

93 . What is the need for finally block?

94 . In what scenarios is code in finally not executed?

95 . Will finally be executed in the program below?

96 . Is try without a catch is allowed?

97 . Is try without catch and finally allowed?

98 . Can you explain the hierarchy of exception handling classes?

99 . What is the difference between error and exception?

100 . What is the difference between checked exceptions and unchecked exceptions?

101 . How do you throw an exception from a method?

102 . What happens when you throw a checked exception from a method?

103 . What are the options you have to eliminate compilation errors when handling checked exceptions?

104 . How do you create a custom exception?

105 . How do you handle multiple exception types with same exception handling block?

106 . Can you explain about try with resources?

107 . How does try with resources work?

108 . Can you explain a few exception handling best practices?

Miscellaneous topics

109 . What are the default values in an array?

110 . How do you loop around an array using enhanced for loop?

111 . How do you print the content of an array?

112 . How do you compare two arrays?

113 . What is an enum?

114 . Can you use a switch statement around an enum?

115 . What are variable arguments or varargs?

116 . What are asserts used for?

117 . When should asserts be used?

118 . What is garbage collection?

119 . Can you explain garbage collection with an example?

120 . When is garbage collection run?

121 . What are best practices on garbage collection?

122 . What are initialization blocks?

123 . What is a static initializer?

124 . What is an instance initializer block?

125 . What is tokenizing?

126 . Can you give an example of tokenizing?

127 . What is serialization?

128 . How do you serialize an object using serializable interface?

129 . How do you de-serialize in Java?

130 . What do you do if only parts of the object have to be serialized?

131 . How do you serialize a hierarchy of objects?

132 . Are the constructors in an object invoked when it is de-serialized?

133 . Are the values of static variables stored when an object is serialized?

Collections

134 . Why do we need collections in Java?

135 . What are the important interfaces in the collection hierarchy?

136 . What are the important methods that are declared in the collection interface?

137 . Can you explain briefly about the List interface?

138 . Explain about ArrayList with an example?

139 . Can an ArrayList have duplicate elements?

140 . How do you iterate around an ArrayList using iterator?

141 . How do you sort an ArrayList?

142 . How do you sort elements in an ArrayList using comparable interface?

143 . How do you sort elements in an ArrayList using comparator interface?

144 . What is vector class? How is it different from an ArrayList?

145 . What is linkedList? What interfaces does it implement? How is it different from an ArrayList?

146 . Can you briefly explain about the Set interface?

147 . What are the important interfaces related to the Set interface?

148 . What is the difference between Set and sortedSet interfaces?

149 . Can you give examples of classes that implement the Set interface?

150 . What is a HashSet?

151 . What is a linkedHashSet? How is different from a HashSet?

152 . What is a TreeSet? How is different from a HashSet?

153 . Can you give examples of implementations of navigableSet?

154 . Explain briefly about Queue interface?

155 . What are the important interfaces related to the Queue interface?

156 . Explain about the Deque interface?

157 . Explain the BlockingQueue interface?

158 . What is a priorityQueue?

159 . Can you give example implementations of the BlockingQueue interface?

160 . Can you briefly explain about the Map interface?

161 . What is difference between Map and sortedMap?

162 . What is a HashMap?

163 . What are the different methods in a Hash Map?

164 . What is a TreeMap? How is different from a HashMap?

165 . Can you give an example of implementation of navigableMap interface?

166 . What are the static methods present in the collections class?

Advanced collections

167 . What is the difference between synchronized and concurrent collections in Java?

168 . Explain about the new concurrent collections in Java?

169 . Explain about copyonwrite concurrent collections approach?

170 . What is compareandswap approach?

171 . What is a lock? How is it different from using synchronized approach?

172 . What is initial capacity of a Java collection?

173 . What is load factor?

174 . When does a Java collection throw UnsupportedOperationException?

175 . What is difference between fail-safe and fail-fast iterators?

176 . What are atomic operations in Java?

177 . What is BlockingQueue in Java?

Generics

178 . What are Generics?

179 . Why do we need Generics? Can you give an example of how Generics make a program more flexible?

180 . How do you declare a generic class?

181 . What are the restrictions in using generic type that is declared in a class declaration?

182 . How can we restrict Generics to a subclass of particular class?

183 . How can we restrict Generics to a super class of particular class?

184 . Can you give an example of a generic method?

Multi threading

185 . What is the need for threads in Java?

186 . How do you create a thread?

187 . How do you create a thread by extending thread class?

188 . How do you create a thread by implementing runnable interface?

189 . How do you run a thread in Java?

190 . What are the different states of a thread?

191 . What is priority of a thread? How do you change the priority of a thread?

192 . What is executorservice?

193 . Can you give an example for executorservice?

194 . Explain different ways of creating executor services . 

195 . How do you check whether an executionservice task executed successfully?

196 . What is callable? How do you execute a callable from executionservice?

197 . What is synchronization of threads?

198 . Can you give an example of a synchronized block?

199 . Can a static method be synchronized?

200 . What is the use of join method in threads?

201 . Describe a few other important methods in threads?

202 . What is a deadlock?

203 . What are the important methods in Java for inter-thread communication?

204 . What is the use of wait method?

205 . What is the use of notify method?

206 . What is the use of notifyall method?

207 . Can you write a synchronized program with wait and notify methods?

Functional Programming - Lamdba expressions and Streams

208 . What is functional programming?

209 . Can you give an example of functional programming?

210 . What is a stream?

211 . Explain about streams with an example?

what are intermediate operations in streams?

212 . What are terminal operations in streams?

213 . What are method references?

214 . What are lambda expressions?

215 . Can you give an example of lambda expression?

216 . Can you explain the relationship between lambda expression and functional interfaces?

217 . What is a predicate?

218 . What is the functional interface - function?

219 . What is a consumer?

220 . Can you give examples of functional interfaces with multiple arguments?

New Features

221 . What are the new features in Java 5?

222 . What are the new features in Java 6?

223 . What are the new features in Java 7?

224 . What are the new features in Java 8?

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Who this course is for:

You are learning Java and want to prepare for a Java Interview

You are a Java Beginner and want to test your Java Knowledge

Students who want to add more depth to their Java Knowledge

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