1. What is the output of the following code?
int x = 5;
System.out.println(++x);
a) 5
b) 6
c) Compilation error
d) Runtime error
Answer: b) 6
2. Which keyword is used to prevent a member variable from being serialized?
a) transient
b) static
c) final
d) volatile
Answer: a) transient
3. What is the output of the following code?
String str1 = "hello";
String str2 = "hello";
System.out.println(str1 == str2);
a) true
b) false
c) Compilation error
d) Runtime error
Answer: a) true
4. What is an abstract class?
a) A class that cannot be instantiated
b) A class that can only be instantiated
c) A class that is final
d) A class with no constructor
Answer: a) A class that cannot be instantiated
5. What is polymorphism?
a) The ability of an object to take on many forms
b) The ability of a method to be defined in multiple classes
c) The ability of a variable to be of multiple types
d) The ability of a class to be inherited by multiple classes
Answer: a) The ability of an object to take on many forms
6. Which keyword is used to create a new instance of a class?
a) new
b) this
c) super
d) instance
Answer: a) new
7. What is the output of the following code?
int[] nums = {1, 2, 3};
for (int i = 0; i < nums.length; i++) {
System.out.println(nums[i]);
}
a) 1 2 3
b) 1
2
3
c) Compilation error
d) Runtime error
Answer: b) 1 2 3
8. Which of the following is not a primitive data type in Java?
a) int
b) float
c) char
d) String
Answer: d) String
9. What is inheritance?
a) The ability of a class to implement an interface
b) The ability of a class to contain an object of another class
c) The ability of a class to be derived from another class
d) The ability of a class to have multiple constructors
Answer: c) The ability of a class to be derived from another class
10. What is the output of the following code?
String str = "hello";
System.out.println(str.substring(1, 4));
a) h
b) el
c) ell
d) llo
Answer: c) ell
11. Which keyword is used to exit a for loop?
a) exit
b) break
c) continue
d) return
Answer: b) break
12. What is the output of the following code?
String str = "hello";
for (int i = str.length() - 1; i >= 0; i--) {
System.out.print(str.charAt(i));
}
a) hello
b) olleh
c) hlo
d) Compilation error
Answer: b) olleh
13. Which keyword is used to create an interface?
a) interface
b) extends
c) implements
d) abstract
Answer: a) interface
14. What is encapsulation?
a) The ability of a class to be extended by another class
b) The ability of a class to implement an interface
c) The ability of a class to contain an object of another class
d) The ability of a class to hide its implementation details
Answer: d) The ability of a class to hide its implementation details
15. What is the output of the following code?
int x = 6;
if (x < 5) {
System.out.println("Less than 5");
} else if (x < 10) {
System.out.println("Between 5 and 10");
} else {
System.out.println("Greater than or equal to 10");
}
a) Less than 5
b) Between 5 and 10
c) Greater than or equal to 10
d) Compilation error
Answer: b) Between 5 and 10
16. Which keyword is used to access a static method or variable?
a) static
b) private
c) public
d) this
Answer: a) static
17. What is a constructor?
a) A method used to create an object
b) A method used to destroy an object
c) A method used to access an object’s properties
d) A method used to declare an object’s class
Answer: a) A method used to create an object
18. What is the output of the following code?
int x = 2;
switch(x) {
case 1:
System.out.println("One");
break;
case 2:
System.out.println("Two");
break;
default:
System.out.println("Default");
break;
}
a) One
b) Two
c) Default
d) Compilation error
Answer: b) Two
19. Which keyword is used to access a parent class’s method or variable?
a) extends
b) super
c) this
d) implements
Answer: b) super
20. What is the output of the following code?
int x = 2;
while (x < 5) {
System.out.println(x);
x++;
}
a) 2 3 4
b) 2 3 4 5
c) 3 4
d) 3 4 5
Answer: a) 2 3 4
21. Which keyword is used to declare an abstract method?
a) abstract
b) final
c) static
d) private
Answer: a) abstract
22. What is the output of the following code?
String str = "hello";
System.out.println(str.indexOf("l"));
a) 2
b) 3
c) 4
d) -1
Answer: b) 3
23. Which keyword is used to create a constant variable?
a) final
b) static
c) volatile
d) transient
Answer: a) final
24. What is the output of the following code?
int x = 5;
if (x > 3 && x < 7) {
System.out.println("In range");
} else {
System.out.println("Out of range");
}
a) In range
b) Out of range
c) Compilation error
d) Runtime error
Answer: a) In range
25. What is a static method?
a) A method that can be accessed without creating an object of the class
b) A method that can only be accessed by objects of the class
c) A method that is final
d) A method that is abstract
Answer: a) A method that can be accessed without creating an object of the class
26. What is the output of the following code?
int x = 10;
do {
System.out.println(x);
x--;
} while (x > 5);
a) 10 9 8 7 6 5
b) 10 9 8 7 6
c) 9 8 7 6
d) Compilation error
Answer: b) 10 9 8 7 6
27. Which keyword is used to declare a synchronized method?
a) synchronized
b) static
c) final
d) volatile
Answer: a) synchronized
28. What is the output of the following code?
int x = 2;
System.out.println(x++);
a) 2
b) 3
c) Compilation error
d) Runtime error
Answer: a) 2
29. What is the difference between an interface and an abstract class?
a) An interface cannot have any method implementations, while an abstract class can have some method implementations
b) An abstract class cannot have any method implementations, while an interface can have some method implementations
c) An abstract class can be instantiated, while an interface cannot be instantiated
d) An interface cannot be extended, while an abstract class can be extended
Answer: a) An interface cannot have any method implementations, while an abstract class can have some method implementations
30. What is a package in Java?
a) A container for classes and other packages
b) A keyword that tells the compiler to import a class
c) A keyword that indicates the start of a block of code
d) A keyword that indicates the end of a block of code
Answer: a) A container for classes and other packages
31. What is the output of the following code?
int x = 2;
int y = x == 2 ? 5 : 7;
System.out.println(y);
a) 5
b) 7
c) Compilation error
d) Runtime error
Answer: a) 5
32. Which keyword is used to specify a variable as a reference to an object?
a) obj
b) ref
c) this
d) none of the above
Answer: d) none of the above
33. What is the output of the following code?
String str = "hello";
System.out.println(str.toUpperCase());
a) hello
b) HELLO
c) Compilation error
d) Runtime error
Answer: b) HELLO
34. Which keyword is used to declare a variable that cannot be changed?
a) final
b) static
c) volatile
d) transient
Answer: a) final
35. What is a thread?
a) A container for code and data
b) A unit of execution within a process
c) A keyword that indicates the start of a block of code
d) A keyword that indicates the end of a block of code
Answer: b) A unit of execution within a process
36. What is the output of the following code?
for (int i = 0; i < 5; i) {
System.out.println(i);
}
a) Compilation error
b) 0 1 2 3 4
c) Infinite loop
d) Runtime error
Answer: c) Infinite loop
37. Which keyword is used to declare a method that cannot be overridden?
a) final
b) static
c) synchronized
d) abstract
Answer: a) final
38. What is the output of the following code?
int x = 1;
int y = 2;
System.out.println(x + y);
a) 1
b) 2
c) 3
d) Compilation error
Answer: c) 3
39. Which keyword is used to import a class into a Java program?
a) import
b) package
c) class
d) none of the above
Answer: a) import
40. What is the output of the following code?
int x = 1;
int y = 2;
System.out.println(x > y ? x : y);
a) 1
b) 2
c) Compilation error
d) Runtime error
Answer: b) 2
41. Which keyword is used to declare an inner class?
a) class
b) private
c) protected
d) none of the above
Answer: d) none of the above (an inner class is declared within another class)
42. What is the output of the following code?
String str = "hello";
System.out.println(str.length());
a) 5
b) 6
c) Compilation error
d) Runtime error
Answer: a) 5
43. Which keyword is used to create a new instance of an array?
a) new
b) this
c) super
d) instance
Answer: a) new
44. What is the output of the following code?
int x = 5;
if (x == 5) {
int y = 2;
System.out.println(y);
}
a) 2
b) Compilation error
c) Runtime error
d) No output
Answer: a) 2
45. What is the output of the following code?
String str1 = "hello";
String str2 = "world";
System.out.println(str1 + " " + str2);
a) helloworld
b) hello world
c) Compilation error
d) Runtime error
Answer: b) hello world
46. Which keyword is used to declare a variable that can be accessed by any object of the class?
a) private
b) protected
c) public
d) none of the above
Answer: c) public
47. What is the output of the following code?
int[] nums = {1, 2, 3};
System.out.println(nums[1]);
a) 1
b) 2
c) 3
d) Compilation error
Answer: b) 2
48. Which keyword is used to declare that a method can throw an exception?
a) try
b) catch
c) throw
d) throws
Answer: d) throws
49. What is the output of the following code?
int x = 2;
System.out.println(x--);
a) 2
b) 1
c) Compilation error
d) Runtime error
Answer: a) 2
50. What is the difference between a while loop and a do-while loop?
a) A while loop checks the condition before executing the loop body, while a do-while loop checks the condition after executing the loop body
b) A do-while loop checks the condition before executing the loop body, while a while loop checks the condition after executing the loop body
c) A while loop can only be executed once, while a do-while loop can be executed multiple times
d) There is no difference between a while loop and a do-while loop
Answer: a) A while loop checks the condition before executing the loop body, while a do-while loop checks the condition after executing the loop body
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