Java MCQ Questions Answers

1. A function that defines the steps necessary to instantiate one object of that class is called:

2. Will a program compile if the main method is defined private?

3. How many objects are created: String s1='String'; String s2='String'; String s3='String';

4. How do we compare enum types in java

5. If you need to determine exactly which class your object is:

6. Which java class provides variables local to each thread?

7. Which method is used to force one thread to wait for another thread to finish?

8. What does the synchronized keyword on a method do?

9. Which is true for interface variables.

10. The @Override annotation

11. The StringBuffer and StringBuilder classes in Java are optimized for

12. A deadlock error occurs when a Java program

13. Output of below code String a='abc'; String b='abc'; String c=new String('abc'); if(a==c && a.equals(b)){ System.out.println('They are equal'); } else System.out.println('They are not equal');

14. public class A { private int m = 5; class N { private int m = 3; public void print() { System.out.println('m=' + m); } } public static void main(String[] args) { A a = new A(); N n = a.new N(); n.print(); } } What is the output?

15. Can static and abstract keywords be used together?

16. You read the following statement in a valid Java program: submarine.dive(depth); What must be true?

17. What's wrong with the following method: public static int getSize(){ int temp = super.getSize(); if(temp==0) temp=this.size; return temp; }

18. Which statement is wrong?

19. Are primitive data types passed by reference or passed by value?

20. The pattern described below is known as: public class Foo{ private static Foo instance; private Foo(){ } private static getInstance(){ if (instance == null){ instance = new Foo(); } return instance; }

21. Which JNDI properties provide security information?

22. How do you declare a destructor in Java?

23. Can an interface have member variables?

24. Will a program run if the main() is not static?

25. A JavaBean is a special Java class:

26. Do we need to import the java.lang package at anytime?

27. Which is correct way of importing an entire package ‘pkg’?

28. which is a correct statement:

29. What is the syntax for creating a class derived from the class named MyClass?

30. What is the proper syntax for a Java class's main method?

31. Which keyword is used to define packages in Java?

32. Do you need to explicitly define a constructor for every class?

33. What are the core JMS-related objects required for each JMS-enabled application?

34. When you run a Java program, the system is running the Java Runtime Engine (JRE) as an executable which then:

35. _____ jumps out of an entire loop, whereas _____ jumps to the next iteration.

36. Consider the following code snippet String river = new String(“Columbia”); System.out.println(river.length()); What is printed?

37. The correct operator for 'conditional or' is:

38. Consider public class MyClass{ public MyClass(){/*code*/} // more code... } To instantiate MyClass, you would write?

39. Which keywords would you use to handle exceptions in Java?

40. The process of changing a datatype of a value is called:

41. The varargs method: public void foo(String... strings) may be called with:

42. public class Dog extends Animal{ ... } is an example of...

43. Which is the correct signature for a main method that can be used as an entry point by the Java runtime?

44. All Java files must have a .java extension and are compiled with the:

45. Class definitions in Java can have which access levels?

46. An applet can do which of the following?

47. You can use the 'static' keyword for which of the following?

48. As a general syntax rule, Java is case sensitive on:

49. What keyword is used to add external package members to the current Java file?

50. Which is correct for the 'main' method of a class?

51. What company developed java?

52. What effect does declaring a method as final have?

53. If I write return at the end of the try block, will the finally block still execute?

54. Under the strictest definition, an interface may contain only:

55. How do you prevent a class from being extended by a subclass?

56. Can you declare an abstract class with no abstract methods?

57. ________ is when a subclass implements a method that is already provided by a superclass.

58. What is a token?

59. What is displayed when the following code is compiled and executed? String s1 = new String('Test'); String s2 = new String('Test'); if (s1==s2) System.out.println('Same'); if (s1.equals(s2)) System.out.println('Equals');

60. A method is considered to be overloaded when:

61. Suppose ArrayList x contains two strings [Beijing, Singapore]. Which method will cause the list to become [Beijing, Chicago, Singapore]?

62. Can we override a static method?

63. Java allows you to specify two types of variables: primitive, which store a single value, and

64. output of program class Test {T obj; Test(T obj) { this.obj=obj } T getobj() {return obj; } } class RunC {public static void main(String[] ar) { Test obj=new Test('hello'); System.out.print(obj.getobj()); } }

65. Can a class be both abstract and final?

66. Which Map implementation is safe for modification in a multi-threaded program?

67. TreeMap class is used to implement which collection interface?

68. Which primitive types is unsigned?

69. Can you mark an interface as final?

70. Difference between Vector and ArrayList?

71. Any valid program compiled under one version of Java...

72. Which is *not* a method in java.lang.String?

73. What is the command to run an executable JAR file named program.jar?

74. The 'synchronized' keyword does the following

75. If 'A' is a class, then what does the statement 'A a1;' do?

76. Can a non-generic class have a generic constructor?

77. Java's Reflection feature allows you to do things including (but not limited to) :

78. What is transient variable?

79. The foreach loop in Java is constructed as:

80. Java programs must have at least one method called main() _____.

81. If you set one object variable equal to another object variable:

82. If you override method 'equals()', what other function you must override for the class to work properly?

83. String objects in Java are immutable which means:

84. Which keyword is used to manually clean up memory in java?

85. Consider the following code: int i=aReader.read(); What is the true of the type of variable aReader?

86. Any source code valid for one version of Java is also valid for all previous versions of Java.

87. What is an abstract class?

88. In Math and other java.lang Classes, generally all methods are declared _.

89. Which method is used to sort a Collection by natural order of its elements?

90. What is the keyword to forbid the serialization of an instance field?

91. Java interfaces can extend...

92. SWING Toolkit contains

93. Is 'main' a keyword in Java?

94. Which is the wildcard symbol for use in generic type specification?

95. what are the parts of JNDI architecture

96. public class SomeClass { public static void main(String[] args) { System.out.println((String)null); } } What is the result of the following program?

97. Non-static attributes can be accessed without an instance of the class.

98. public class SomeClass { public static void main(String[] args) { System.out.println(((String)null).toUpperCase()); } } What is the result of the following program?

99. Are static fields of a class included in serialization?

100. What does a synchronized method use as a mutex in Java?