Java Classes and Objects Interview MCQ Questions and Answers 2 | MCQ Questions and Answers on Java Classes and Objects.
blog.softwaretechit.com
home.softwaretechit.com
Study and learn Interview MCQ Questions and Answers on Java Classes and Objects. Attend job interviews easily with these Multiple Choice Questions. You can print these Questions in default mode to conduct exams directly. You can download these MCQs in PDF format by Choosing Print Option first and Save as PDF option next using any Web Browser.
Go through Java Theory Notes Classes and Java Theory Notes on Objects before reading these objective questions.
1) What is the output of the below Java program with two classes?
//Testing1.java
public class Example
{
}
public class Testing1
{
public static void main(String[] args)
{
System.out.println(“Hello Boss.!”);
}
}
A) Hello Boss.!
B) No Output
C) Compiler error
D) None of the above
Answer [=]
C
Explanation:
There can not be more than one public class declared inside a single java file.
2) What is the output of the below Java program?
//bingo.java file
public class Hello
{
public static void main(String[] args)
{
System.out.println(“BINGO”);
}
}
A) bingo
B) BINGO
C) Compiler error
D) None
Answer [=]
C
Explanation:
The class name and the java file name should be the same. So, change either file name or class name to match.
3) State TRUE or FALSE. A Java class provides encapsulation.
A) TRUE
B) FALSE
C) –
D) –
Answer [=]
A
4) What is the output of the below java class?
class Fox
{
int legs = 2;
}
class Testing2
{
public static void main(String[] args)
{
Fox t1 = new Fox();
System.out.println(“T1 before: ” + t1.legs);
t1.legs = 4;
System.out.println(“T1 After: ” + t1.legs);
}
}
A)
T1 before: 4
T1 After: 4
B)
T1 before: 2
T1 After: 2
C)
T1 before: 2
T1 After: 4
D) Compiler error
Answer [=]
C
Explanation:
There can be any number of classes in a single .java file.
5) The value of one primitive variable is assigned to another primitive variable by ___ in Java.
A) Pass by value
B) Pass by reference
C) –
D) –
Answer [=]
A
6) A primitive variable is passed from one method to another method by ___ in Java.
A) Pass by value
B) Pass by reference
C) –
D) –
Answer [=]
A
7) An object or primitive value that is passed from one method to another method is called ___ in Java. (Argument / Parameter)
A) Argument
B) Parameter
C) –
D) –
Answer [=]
B
8) An object or a primitive value that is received in a method from another method is called ___ in Java. (Argument / Parameter)
A) Argument
B) Parameter
C) –
D) –
Answer [=]
A
9) What is the output of the below Java program that passes an object to another method?
class Food
{
int items;
int show()
{return items;}
}
class Testing9
{
public static void main(String[] args)
{
Food f = new Food();
f.items = 5;
System.out.println(“Items Before = ” + f.show());
change(f);
System.out.println(“Items After = ” + f.show());
}
static void change(Food foo)
{ foo.items = 10; }
}
A)
Items Before = 10
Items After = 10
B)
Items Before = 5
Items After = 5
C)
Items Before = 5
Items After = 10
D)
Items Before = 10
Items After = 5
Answer [=]
C
10) What is the output of the below Java program that passes primitive values?
class Testing10
{
int rats = 5;
public static void main(String[] args)
{
Testing10 t1 = new Testing10();
System.out.println(“Rats Before = ” + t1.rats);
modify(t1.rats);
System.out.println(“Rats After = ” + t1.rats);
}
static void modify(int r)
{ r = 20; }
}
A)
Rats Before = 5
Rats After = 5
B)
Rats Before = 20
Rats After = 20
C)
Rats Before = 5
Rats After = 20
D)
Rats Before = 20
Rats After = 5
Answer [=]
A
Explanation:
The primitive values are passed by value only. So, changes in the method modify does not change the original value.
11) Java object assignment happens by ___.
A) Pass by Value
B) Pass by Reference
C) –
D) –
Answer [=]
B
Explanation:
Yes. That is the reason why you can change the values of variables of the object using another reference.
12) Java object passing from one method to another method happens by ___.
A) Pass by Value
B) Pass by Reference
C) –
D) –
Answer [=]
B
Explanation:
References point to the original objects. So they can change the state of the objects.
13) In Java Pass by reference ___ is passed even if you are passing a reference to an object.
A) Address value
B) Variable value
C) Hash code
D) None of the above
Answer [=]
A
Explanation:
Yes. The address is passed automatically by Java. So, Java pundits argue that it is passing a value (Address).
14) A Java reference is comparable to ___ in C language.
A) Enum
B) Structure
C) Pointer
D) None
Answer [=]
C
15) ___ is the superclass to all Java classes either user-defined or built-in.
A) Class
B) Object
C) Superclass
D) Null
Answer [=]
B
Explanation:
Yes. java.lang.Object is the superclass to all Java classes.
16) State TRUE of FALSE. Java objects have built-in methods to handle threads.
A) TRUE
B) FALSE
C) –
D) –
Answer [=]
A
Explanation:
Yes. The methods are wait(), notify() and notifyAll().
17) State TRUE or FALSE. Java Object’s hashcode() method is mainly used with Collection objects.
A) TRUE
B) FALSE
C) –
D) –
Answer [=]
A
Explanation:
Java collection classes use the hashcode() method to determine the equality of two objects.
18) What is the output of the below Java program using toString() method?
class College
{
public String toString()
{ return “College Object”; }
}
class Testing18
{
public static void main(String[] args)
{
College col = new College();
System.out.println(“Printing Object=” + col);
}
}
A) Printing Object=
B) Printing Object=null
C) Printing Object=College Object
D) Compiler error
Answer [=]
C
Explanation:
print() and println() methods call toString() method of objects automatically.
19) What is the output of the below Java program?
class Cricket
{ int runs; }
class Testing19
{
public static void main(String[] args)
{
Cricket c1 = new Cricket();
c1.runs = 250;
Cricket c2;
c2 = c1;
c2.runs = 300;
System.out.println(“Runs= ” + c1.runs);
}
}
A) Runs= 0
B) Runs= 250
C) Runs= 300
D) Compiler error
Answer [=]
C
Explanation:
The reference C2 also points to the same object pointed by reference C1.
20) What is the output of the below Java program?
class WordPress
{ int posts; }
class Testing20
{
public static void main(String[] args)
{
WordPress wp1 = new WordPress();
wp1.posts = 25;
WordPress wp2 = wp1;
wp1 = null;
System.out.println(“Posts=” + wp2.posts);
}
}
A) Posts=25
B) Posts=0
C) Posts=null
D) Runtime exception occurs
Answer [=]
A
Explanation:
Even if one REFERENCE to the same object is alive, it can be used to access the object. So, wp2 still works even if wp1 is set to null.
