study guides for every class

that actually explain what's on your next test

Extends

from class:

AP Computer Science A

Definition

In Java, the keyword "extends" is used to create a subclass that inherits properties and methods from a superclass. It establishes an "is-a" relationship between classes.

congrats on reading the definition of extends. now let's actually learn it.

ok, let's learn stuff

"Extends" also found in:

Practice Questions (20)

If class C extends class H, class B extends class H, and class G extends class B, what is the relationship between H and G?
Given the following code: ``` class A { public static void show() { System.out.print("A"); } } class B extends A { public static void show() { System.out.print("B"); } } class C extends B { public static void show() { System.out.print("C"); } } ``` What will be the output when the following code is executed? ``` A obj1 = new C(); B obj2 = new C(); C obj3 = new C(); obj1.show(); obj2.show(); obj3.show(); ```
Given the following code: ``` class A { public void display() { System.out.print("A"); } } class B extends A { public void display() { System.out.print("B"); } } class C extends B { public void display() { System.out.print("C"); } } ``` What will be the output when the following code is executed? ``` B obj1 = new C(); C obj2 = new C(); A obj3 = new C(); obj1.display(); obj2.display(); obj3.display(); ```
Given the following code: ``` class A { public void show() { System.out.println("A"); } } class B extends A { public void show() { System.out.println("B"); } } class C extends B { public void show() { System.out.println("C"); } } ``` What will be the output when the following code is executed? ``` A obj = new C(); obj.show(); ```
Consider the following class hierarchy: ``` class Animal { void makeSound() { System.out.println("Some sound"); } } class Dog extends Animal { void makeSound() { System.out.println("Bark"); } } class Cat extends Animal { void makeSound() { System.out.println("Meow"); } } ``` If we create an object like this: `Animal animal = new Dog();`, what will be printed when we call `animal.makeSound()`?
Given the following code: ``` class A { public static void printMessage() { System.out.println("Hi from A"); } } class B extends A { public static void printMessage() { System.out.println("Hi from B"); } } ``` What will be the output when the following code is executed? ``` B obj = new B(); obj.printMessage(); ```
What will be the output when the following code is executed? ``` public class A { public void print() { System.out.println("A"); } } public class B extends A { public void print() { System.out.println("B"); } } public class C extends B { public void print() { System.out.println("C"); } } public class Main { public static void main(String[] args) { A obj = new C(); obj.print(); } } ```
Given the following code: ``` class A { public void show() { System.out.println("A"); } } class B extends A { public void show() { System.out.println("B"); } } ``` What will be the output when the following code is executed? ``` A obj1 = new A(); B obj2 = new B(); A obj3 = new B(); obj1.show(); obj2.show(); obj3.show(); ```
Given the block of code below, answer the following question: ```java class Person { // constructor not shown public void printGreeting() { System.out.println("Hello! How are you?"); } } class Student extends Person { // constructor not shown } ``` Question: Consider the code above. If we create an object of the `Student` class and call the `printGreeting()` method on that object, what will be outputted?
"Given the block of code below, answer the following question: ```java class Shape { // constructor not shown public void draw() { System.out.println("Drawing a shape"); } } class Circle extends Shape { // constructor not shown public void draw() { System.out.println("Drawing a circle"); super.draw(); } } ``` Question: Consider the code above. If we create an object of the Circle class and call the `draw()` method on that object, what will be the output?
Consider the code below. If we create an object of the B class and call the `printMessage()` method on that object, what will be the output? ```java class B { void printMessage() { super.printMessage(); System.out.println("Hello from B"); } } class A extends B { void printMessage() { System.out.println("Hello from A"); } } ```
Consider the code below. If we create an object of the Child class and call the `printMessage()` method on that object, what will happen? ```java class Parent { void printMessage() { System.out.println("Hello from Parent"); } } class Child extends Parent { void printMessage() { printMessage(); System.out.println("Hello from Child"); } } ```
If Class D extends Class B, and Class C extends Class D, what is the relationship between Class C and Class B?
What output do we get if we run the following code? class X { public X() { System.out.println("X's no-argument constructor is invoked"); } } class Y extends X { public Y() { } } public class Z { public static void main(String[] args) { Y y = new Y(); } }
What happens when we try to run the following? class D { public D(int x) { } } class E extends D { public E() { } } public class C { public static void main(String[] args) { E e = new E(); } }
Given the block of code below, answer the following question: ```java class Shape { // constructor not shown public void draw() { System.out.println("Drawing a shape"); } } class Circle extends Shape { // constructor not shown @Override public void draw() { System.out.println("Drawing a circle"); } } ``` Question: Consider the code above. If we create an object of the Circle class and call the `draw()` method on that object, what will be the output?
Given the block of code below, answer the following question: ```java class Vehicle { // constructor not shown public void startEngine() { System.out.println("Vrooom!"); } } class Car extends Vehicle { // constructor not shown public void reverse() { System.out.println("Beep! Beep!"); } } ``` Question: Consider the code above. If we create an object of the `Car` class and call the `startEngine()` method on that object, what will be outputted?
Given the block of code below, answer the following question: ```java class Animal { // constructor not shown } class Dog extends Animal { // constructor not shown public void makeSound() { System.out.println("Woof! Woof!"); } } ``` Question: Consider the code above. If we create an object of the `Dog` class and call the `makeSound()` method on that object, what will be outputted?
What does the class header “public class B extends C” mean?
If classes E and F are created using the headers “public class E extends C” and “public class F extends C” respectively, what is true about them?

study guides for every class

that actually explain what's on your next test

Extends

from class:

AP Computer Science A

Definition

"Extends" also found in:

Practice Questions (20)

© 2024 Fiveable Inc. All rights reserved.

AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.

Back

Next

study guides for every class

that actually explain what's on your next test

Extends

from class:

AP Computer Science A

Definition

Related terms

"Extends" also found in:

Practice Questions (20)

© 2024 Fiveable Inc. All rights reserved.

AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.

Back

Next