Java MCQs on access control of Java Programming Language.
1. Which of these access specifiers must be used for main() method? Answer: b 2. Which of these is used to access a member of class before object of that class is created? Answer: c 3. Which of these is used as a default for a member of a class if no access specifier is used for it? Answer: a 4. What is the process by which we can control what parts of a program can access the members of a class? Answer: c 5. Which of the following statements are incorrect? Answer: c 6. What will be the output of the following Java code? a) 3 3 7. What will be the output of the following Java code? a) 2 3 8. What will be the output of the following Java code? a) 7 7.4 9. Which of these access specifier must be used for class so that it can be inherited by another subclass? Answer: a
a) private
b) public
c) protected
d) none of the mentioned
Clarification: main() method must be specified public as it called by Java run time system, outside of the program. If no access specifier is used then by default member is public within its own package & cannot be accessed by Java run time system.
a) public
b) private
c) static
d) protected
Clarification: None.
a) private
b) public
c) public, within its own package
d) protected
Clarification: When we pass an argument by call-by-value a copy of argument is made into the formal parameter of the subroutine and changes made on parameters of subroutine have no effect on original argument, they remain the same.
a) Polymorphism
b) Abstraction
c) Encapsulation
d) Recursion
Clarification: None.
a) public members of class can be accessed by any code in the program
b) private members of class can only be accessed by other members of the class
c) private members of class can be inherited by a subclass, and become protected members in subclass
d) protected members of a class can be inherited by a subclass, and become private members of the subclass
Clarification: private members of a class can not be inherited by a subclass.
class access
{
public int x;
private int y;
void cal(int a, int b)
{
x = a + 1;
y = b;
}
}
public class access_specifier
{
public static void main(String args[])
{
access obj = new access();
obj.cal(2, 3);
System.out.println(obj.x + " " + obj.y);
}
}
b) 2 3
c) Runtime Error
d) Compilation Error
Clarification: None.
output:
$ javac access_specifier.java
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
The field access.y is not visible
class access
{
public int x;
private int y;
void cal(int a, int b)
{
x = a + 1;
y = b;
}
void print()
{
System.out.println(" " + y);
}
}
public class access_specifier
{
public static void main(String args[])
{
access obj = new access();
obj.cal(2, 3);
System.out.println(obj.x);
obj.print();
}
}
b) 3 3
c) Runtime Error
d) Compilation Error
Clarification: None.
output:
$ javac access_specifier.java
$ java access_specifier
3 3
class static_out
{
static int x;
static int y;
void add(int a, int b)
{
x = a + b;
y = x + b;
}
}
public class static_use
{
public static void main(String args[])
{
static_out obj1 = new static_out();
static_out obj2 = new static_out();
int a = 2;
obj1.add(a, a + 1);
obj2.add(5, a);
System.out.println(obj1.x + " " + obj2.y);
}
}
b) 6 6.4
c) 7 9
d) 9 7
Clarification: None.
output:
$ javac static_use.java
$ java static_use
7 9
a) public
b) private
c) protected
d) none of the mentioned
Clarification: None.