Computer Science : Computer Science
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Example Questions
Example Question #11 : Class Design
Which of the following is TRUE about the Object class?
Object is the only class that never has any descendants.
None of these answers are true.
Object inherits a minimum of four classes.
Object has one superclass, Entity.
Every class has all of Object's methods.
Every class has all of Object's methods.
Object is the most basic class which all others, even user made ones, inherit. Therefore, all classes have Object's methods. A way to think of classes is to think of a tree: the Object class is the lowest node on the tree, where all other nodes can connect back to.
Example Question #4 : Class Inheritance
True or False.
The class BetterMan inherits from the class Man.
public class BetterMan extends Man {
}
False
True
True
The class BetterMan inherits methods from the class man. The keyword "extends" means that BetterMan will get all the methods from Man plus be able to extend the class by adding its own methods. All methods from Man can be used in BetterMan by calling the keyword better.
Example Question #21 : Class Design
What does the code print?
class Parent{ final public void show() {
System.out.println("Parent::show() called");
}
} class Child extends Parent {
public void show() {
System.out.println("Child::show() called");
}
} public class Main {
public static void main(String[] args) {
Parent parent = new Child();
parent.show();
}
}Runtime Error
Compiler Error
Parent::show() called
Parent::show() called
Child::show() called
Child::show() called
Compiler Error
Final methods can't be overriden. So the code won't compile because of this. Now if the final modifier were to be removed. The code would compile and run and produce:
Child::show()
Example Question #3 : Class Inheritance
class Pet {
public:
Pet() {}
virtual void bar() {cout << "In pet bar(); }
};
class Cat : public Pet {
public:
virtual void eat() {cout << "Cat eating"; }
virtual void bar() {cout << "In Cat bar()"; }
};
Given the above classes, what would the result of:
int main(){
Pet * petPtr = new Cat();
petPtr -> eat();
}
None of these
Compilation error
The program compiles but has a runtime error
The program runs and prints: "Pet eating"
The program runs and prints: "Cat eating"
Compilation error
When a child class inherits the properties of a parent class, some attributes are inherited and some aren't. In C++, the constructor of the parent class is not inherited. The Cat class does not have a constructor therefore the program will not compile.
Example Question #301 : Computer Science
Consider the code below:
private static class Philosopher {
private String name;
private String favoriteSubject;
public Philosopher(String n, String f) {
name = n;
favoriteSubject = f;
}
public String getName() {
return name;
}
public String getFavoriteSubject() {
return favoriteSubject;
}
public void speak() {
System.out.println("Hello, World! My name is "+name + ". My favorite subject is "+favoriteSubject);
}
}
private static class Nominalist extends Philosopher {
boolean franciscan;
public Nominalist(String n,boolean frank) {
super(n,"logic");
franciscan = frank;
}
public void speak() {
super.speak();
if(franciscan) {
System.out.println("I am a Franciscan");
} else {
System.out.println("I am not a Franciscan");
}
}
public String whoMightHaveTaughtMe() {
if(franciscan) {
return "Perhaps William of Ockham?....";
} else {
return "Perhaps it was Durandus of St. Pourçain — scandalous, a Dominican nominalist!";
}
}
}
If you wished to make a toString() method for both Philosopher and Nominalist, using the same output as in each class' current speak() methods, what would be the best way to organize your code?
I. Have toString() invoke both classes' speak() methods.
II. Have the speak() method invoke the new toString() method.
III. Create a new subclass and write the toString() method in that.
III
II
I
I and III
II
The toString() method must return a string value. Therefore, it makes the most sense that you would have this method generate the output that you currently generate in speak(). Then, you could have speak() invoke the toString() method to output the same string data.
Example Question #302 : Computer Science
Given a class Thing and the code:
Thing thingOne, thingTwo;
What function call is the following equivalent to?
thingTwo = thingOne;
ostream& Thing::operator=(const Thing& rhs);
thingOne uses the copy constructor of thingTwo
thingTwo.operator = (thingOne);
operator=(thingTwo, thingOne);
None of the above
thingTwo.operator = (thingOne);
What's given to us is that thingOne and thingTwo have already been created, this is a vital piece of information. Let's go through each of the choices
operator=(thingTwo, thingOne);
This line of code makes no sense and is syntactically wrong.
ostream& Thing::operator=(const Thing& rhs);
This line of code says to access the "operator=" method from the "Thing" class and put it onto the ostream, this has nothing to do with assigning thingOne to thingTwo.
When we come across the choice of the copy constructor, we have to keep in mind that the copy constructor is only used when an object use to to create another one, for example we have a given class called Foo:
Foo foo;
Foo foobar = foo;
In this case, we are using foo to create foobar.
The only choice that works is:
thingTwo.operator=(thingOne);
This line of code means that the thingOne object is being assigned to thingTwo.
Example Question #301 : Computer Science
Consider the history of the following popular programming languages:
PHP
Java
Objective-C
Python
Which of the following is the closest ancestor shared by ALL of these languages?
Ruby
C
Lisp
Smalltalk
Ada
C
All of these languages are C-based languages.
- Ruby was invented in 1995, the same year as PHP, so it could not have influenced earlier languages like Objective-C and Python.
- Lisp did influence at least one language, Python, but it did not influence any others.
- Ada directly influenced Java, and because it influenced C, it can be argued that it is an ancestor of these other languages; however, because of this, Ada is not the CLOSEST ancestor.
- Smalltalk influenced Objective-C, but no other languages on this list.
A clue was the answer "Objective-C," which is a strict superset of C that adds Object Orientation.
Example Question #303 : Computer Science
What is the value of the string kitchen after the following code is run?
- class home
- {
- public:
- home(string);
- void searchhome();
- int buyhome();
- private:
- string kitchen();
- };
- home::home(string c)
- {
- kitchen=c;
- }
- int main()
- {
- str=’big’;
- home(str);
- }
'small'
str
'big'
void
c
'big'
The constructor here in line 4 of the class definition is where it gets tricky. In the initialization of the constructor, we note that the input is a string.
Going down to line 10, to where the constructor function is defined, we see that a constructor with an input of c, which is defined as a string, will set the value of kitchen to c.
Finally, going down to our main code, we see that the value of the constructor in main is 'big', defined in str.
So kitchen='big'.
Example Question #3 : Program Design
What is the difference between declaring a function as void and declaring it as int?
There is no difference.
A void declaration does not expect an output to that function, whereas an int function declarations expects an intger value as the output to the function.
A void function has no input and an int function has at least one integer input.
A void function can have any return type whereas an int function can only have one return type.
An int function needs to declare an integer variable inside the function and a void function doesn't.
A void declaration does not expect an output to that function, whereas an int function declarations expects an intger value as the output to the function.
Function delcarations are very significant, as you must define what the return type of the function is. A void function doesn't need a return type, whereas the int function must have an integer value as its return type.
Example Question #303 : Computer Science
What's wrong with the following code?
void printsometext()
{
cout<<"printing text\n";
for(int i=0;i<3;i=i+1)
{
cout<<i<<"\n"
}
return 2;
}
You need semicolons after the function declaration.
A void function cannot return an output.
The character \n does not exist.
The loop is formatted incorrectly.
Cout cannot output a number.
A void function cannot return an output.
It is very important when creating a function to select the return type. If you want your function to return an integer, you would place "int" before your function to signify that the function expects an integer output. In this case, the function is declared as void, meaning there is no output. However, the code indicated a return value of 2, which conflicts with the void keyword. To fix this problem, either remove the return statement or change void to int.
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