Java Super: Parent Class

Use the super keyword to access a parent class from a descendant class. Super is used with the extends keyword.

Super. With this keyword, we can reference the "ancestor" or base class of a derived class. Super enables us to access ancestor classes with ease.

Along with the extends keyword, we use super to facilitate object-oriented design. We compose classes from a parent. This sometimes reduces code duplication.Extends Class

First example. Let us examine a "super" program. First notice the "extends" keyword. Here the class Cat extends the class Animal. I call the scratch() method on Cat.

And: The Cat scratch method itself calls its parent scratch method from the Animal class. We call a "super" class method.

Java program that uses super class Animal { public void scratch() { System.out.println("Animal scratched"); } } class Cat extends Animal { public void scratch() { // Call super-class method. super.scratch(); System.out.println("Cat scratched"); } } public class Program { public static void main(String[] args) { // Create cat and call method. Cat cat = new Cat(); cat.scratch(); } } Output Animal scratched Cat scratched

Super, Object. All classes have a parent class of Object. If a class has no "extends" class, it inherits from Object. We can use methods like hashCode() from Object.

Java program that uses super, Object class Page { public void test() { // This class inherits from Object only. // ... So it gains access to methods like hashCode on Object. System.out.println(super.hashCode()); } } public class Program { public static void main(String[] args) { Page page = new Page(); page.test(); } } Output 366712642

Super, constructor. With a call to super() in a derived class, we can invoke the parent's constructor. We can pass arguments to the super() method and they are received in that constructor.

Here: The Image class extends the Data class. We invoke the Data constructor from the Image constructor with super().

Java program that uses super constructor class Data { public Data() { System.out.println("Data constructor"); } } class Image extends Data { public Image() { // Call the superclass constructor. super(); } } public class Program { public static void main(String[] args) { Image value = new Image(); System.out.println("Done"); } } Output Data constructor Done

In other languages like C# we use the "base" keyword instead of super. But the meaning is similar. We use these keywords to reference the parent.

A summary. Class composition is not a fix for all design problems. But it can sometimes help complicated programs become simpler. For small projects, though, it is less often needed.

The Dev Codes

.Net

.NET Array Dictionary List String 2D Async DataTable Dates DateTime Enum File For Foreach Format IEnumerable If IndexOf Lambda LINQ Parse Path Process Property Regex Replace Sort Split Static StringBuilder Substring Switch Tuple

Java

Core Array ArrayList HashMap String 2D Cast Character Console Deque Duplicates File For Format HashSet If IndexOf Lambda Math ParseInt Process Random Regex Replace Sort Split StringBuilder Substring Switch Vector While

TheDeveloperBlog.com

Java Super: Parent Class

Related Links:

.Net

Java

Related Links