Parent and child classes in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a parent class in Java?

A parent class, also called a superclass, is a class that other classes (child classes) inherit from. It provides common properties and methods that child classes can use or override.

beginner

What does it mean when a child class extends a parent class?

When a child class extends a parent class, it means the child inherits all the fields and methods of the parent. The child can use or change these inherited features and add new ones.

intermediate

How can a child class override a method from its parent class?

A child class can provide its own version of a method by defining a method with the same name and parameters. This is called method overriding and allows the child to change behavior.

intermediate

What keyword is used in Java to call a parent class constructor from a child class?

The keyword <code>super</code> is used inside a child class constructor to call the parent class constructor. This helps initialize the parent part of the object.

intermediate

Can a child class access private members of its parent class directly?

No, private members of a parent class are not accessible directly by the child class. They can only be accessed through public or protected methods provided by the parent.

Which keyword is used to create a child class from a parent class in Java?

A inherits

B implements

C extends

D super

The extends keyword is used to create a child class that inherits from a parent class.

What happens when a child class overrides a method from its parent?

A The child class provides its own version of the method.

B The parent method is deleted.

C The method becomes private.

D The child class cannot use the method.

Overriding means the child class gives its own version of the method, replacing the parent's behavior when called on the child.

How can a child class call the constructor of its parent class?

A Using the <code>extends()</code> keyword.

B Using the <code>this()</code> keyword.

C Using the <code>parent()</code> keyword.

D Using the <code>super()</code> keyword.

The super() keyword calls the parent class constructor from the child class.

Can a child class access private fields of its parent class directly?

A Yes, always.

B No, private fields are not accessible directly.

C Only if the child class is in the same package.

D Only if the child class overrides them.

Private fields are hidden from child classes and can only be accessed through public or protected methods.

What is the main benefit of using parent and child classes?

A Code reuse and organization.

B Slower program execution.

C Making code harder to read.

D Preventing any changes to code.

Inheritance allows child classes to reuse code from parent classes, making programs easier to organize and maintain.

Explain how inheritance works between parent and child classes in Java.

Think about how a child can get features from a parent and change them.

Describe how to use the super keyword in a child class constructor.

Remember how to connect child and parent constructors.