Inheriting Methods Flashcards
Define overriding a method !
overriding is when a child class declares a method that has the same signature and return type as the method in its super class and give it a new implementation
When overriding a method, in the child class, how to reference the parent method from the child class ?
When you override a method in the child class, and you want to reference the parent class method from the child class method you have to use the ‘super’ keyword
Explain with an example a common pitfall that you may encounter when referencing a parent overriden method in the child’s overrided method
public double getAverageWeight() {
return getAverageWeight()+20; // INFINITE LOOP
}
In this example, the compiler would not call the parent Canine method; it would call the current Wolf method since it would think you were executing a recursive call.
A recursive function must have a termination condition. In this example, there is no termination condition; therefore, the application will attempt to call itself infinitely and produce a stack overflow error at runtime.
Give a list of checks that the compiler performs when you override a non-private method !
- The method in the child class must have the same signature as the method in the parent class.
- The method in the child class must be at least as accessible or more accessible than the method in the parent class.
- The method in the child class may not throw a checked exception that is new or broader than the class of any exception thrown in the parent class method.
- If the method returns a value, it must be the same or a subclass of the method in the parent class, known as covariant return types.
What is the difference between overloading and overriding ?
Overloading a method and overriding a method are similar in that they both involve redefining a method using the same name
They differ in that an overloaded method will use a different signature than an overridden method.
Give the procedure of verifying that an overridden method is correct!
in order to make sure that a method has been correctly overridden, you have to make sure that it has the same signature, the same return type or a subtype of the return type and doesn’t throw an exception or throws a subtype of the exception, as the parent’s method
Why is it not possible to override a private method in the parent class ?
it is not possible to override a private method in the parent class because it is not accessible from any other class, including its subclasses.
Give me a common pitfall of overriding private methods !
a common pitfall is to think that a child method that has the
same signature and return type as a parent private method is an
overridden method
Define Hiding (methods) !
Hiding methods is defining a static method in the child’s class with
same signature and return type as the static method defined in the parent class
What is the difference between Hiding and Overriding !
The difference between method hiding and method overriding in Java is that method hiding applies exclusively to static methods, where a subclass defines a static method with the same signature as its superclass, while method overriding is specifically for instance methods, allowing a subclass to provide a specialized implementation that supersedes the superclass’s implementation.
Give the rules for Hiding !
Same rules for method overriding + “The method defined in the child class must be marked as static if it is marked as static in the parent class (method hiding). Likewise, the method must not be marked as static in the child class if it is not marked as static in the parent class (method overriding).”
Give an example of a compiler error of a method that should be overridden and not hidden in the child class and vice versa !
public class Bear {
public static void sneeze() {
System.out.println(“Bear is sneezing”);
}
public void hibernate() {
System.out.println(“Bear is hibernating”);
}
}
public class Panda extends Bear {
public void sneeze() { // DOES NOT COMPILE
System.out.println(“Panda bear sneezes quietly”);
}
public static void hibernate() { // DOES NOT COMPILE
System.out.println(“Panda bear is going to sleep”);
}
}
In this example, sneeze() is marked as static in the parent class but not in the child class. The compiler detects that you’re trying to override a method that should be hidden and generates a compiler error
In the second method, hibernate() is an instance member in the parent class but a static method in the child class.
In this scenario, the compiler thinks that you’re trying to hide a method that should be overridden and also generates a compiler error.
Give a characteristic of hidden methods that sets it apart from overridden methods !
a characteristic of hidden methods is that when you use a reference of the parent class type to call the static method of the parent class, it is the class defined in the parent class that gets implemented
Give an important characteristic of final methods !
Final methods cannot be overridden.
This rule is in place both when you override a method and when you hide a method. In other words, you cannot hide a static method in a parent class if it is marked as final.
What is the purpose of making a method final ?
You’d mark a method as Final when you’re defining a parent class and want to guarantee certain behavior of a method in the parent class, regardless of which child is invoking the method.
