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Consider the three classes Alpha, Beta, and Gamma. What is the output of the following code that uses these classes? ArrayList greek = new ArrayList(); greek.add(new Alpha()); greek.add(new Beta()); greek.add(new Alpha()); greek.add(new Beta()); System.out.print(greek.get(2).getOne());

Consider the three classes Alpha, Beta, and Gamma. What is the output of the following code that uses these classes? ArrayList greek = new ArrayList(); greek.add(new Alpha()); greek.add(new Beta()); greek.add(new Alpha()); greek.add(new Beta()); System.out.print(greek.get(2).getOne());

Database System Concepts
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
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**Title: Understanding Class Inheritance in Java: Alpha, Beta, and Gamma** Consider the three classes `Alpha`, `Beta`, and `Gamma`. What is the output of the following code that uses these classes? ### Code Explanation ```java ArrayList<Gamma> greek = new ArrayList<Gamma>(); greek.add(new Alpha()); greek.add(new Beta()); greek.add(new Alpha()); greek.add(new Beta()); System.out.print(greek.get(2).getOne()); ``` ### Class Definitions 1. **Class `Alpha`** ```java public class Alpha extends Gamma { public String getTwo() { return "2"; } public String getTwo(int i) { return "two"; } } ``` 2. **Class `Beta`** ```java public class Beta extends Gamma { public String getThree() { return "3"; } public String getFour() { return "four"; } } ``` 3. **Abstract Class `Gamma`** ```java public abstract class Gamma { public String getOne() { return "1"; } public String getFour() { return "4"; } } ``` ### Explanation of Code Execution - An `ArrayList` named `greek` is created to hold objects of type `Gamma`. - Four objects are added to the `greek` list in the following order: two `Alpha` objects and two `Beta` objects. - The `System.out.print` statement retrieves the third object (`index 2`) from the list, which is an `Alpha` object, and calls the `getOne()` method. ### Output - Since `Alpha` extends `Gamma`, it inherits the method `getOne()` from `Gamma`. - Therefore, the `getOne()` method is executed, and the output is: ``` 1 ``` This simple example demonstrates how inheritance allows objects to use superclass methods, while subclass methods can extend or override functionality when needed.
Transcribed Image Text:**Title: Understanding Class Inheritance in Java: Alpha, Beta, and Gamma** Consider the three classes `Alpha`, `Beta`, and `Gamma`. What is the output of the following code that uses these classes? ### Code Explanation ```java ArrayList<Gamma> greek = new ArrayList<Gamma>(); greek.add(new Alpha()); greek.add(new Beta()); greek.add(new Alpha()); greek.add(new Beta()); System.out.print(greek.get(2).getOne()); ``` ### Class Definitions 1. **Class `Alpha`** ```java public class Alpha extends Gamma { public String getTwo() { return "2"; } public String getTwo(int i) { return "two"; } } ``` 2. **Class `Beta`** ```java public class Beta extends Gamma { public String getThree() { return "3"; } public String getFour() { return "four"; } } ``` 3. **Abstract Class `Gamma`** ```java public abstract class Gamma { public String getOne() { return "1"; } public String getFour() { return "4"; } } ``` ### Explanation of Code Execution - An `ArrayList` named `greek` is created to hold objects of type `Gamma`. - Four objects are added to the `greek` list in the following order: two `Alpha` objects and two `Beta` objects. - The `System.out.print` statement retrieves the third object (`index 2`) from the list, which is an `Alpha` object, and calls the `getOne()` method. ### Output - Since `Alpha` extends `Gamma`, it inherits the method `getOne()` from `Gamma`. - Therefore, the `getOne()` method is executed, and the output is: ``` 1 ``` This simple example demonstrates how inheritance allows objects to use superclass methods, while subclass methods can extend or override functionality when needed.
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