Class SealedClassesPreviewExamples

java.lang.Object

net.jrodolfo.java_evolution.java15.SealedClassesPreviewExamples

public class SealedClassesPreviewExamples
extends Object

Demonstrates sealed classes as a Java 15 preview feature.

Before sealed classes, a type hierarchy was usually open to any subtype that could access the parent type. That made it difficult to model small closed domains directly in the type system.

Sealed classes solve this by letting the parent type explicitly list permitted subtypes. They became final in Java 17. This project compiles on JDK 25, so the example uses final syntax while documenting the Java 15 preview origin.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final record	SealedClassesPreviewExamples.Circle	Circle implementation permitted by SealedClassesPreviewExamples.Shape.
static final record	SealedClassesPreviewExamples.Rectangle	Rectangle implementation permitted by SealedClassesPreviewExamples.Shape.
static interface	SealedClassesPreviewExamples.Shape	Sealed parent type that explicitly lists permitted implementations.

Constructor Summary

Constructors

Constructor	Description
SealedClassesPreviewExamples()

Method Summary

Modifier and Type	Method	Description
double	area(SealedClassesPreviewExamples.Shape shape)	Calculates the area of a known shape hierarchy.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

SealedClassesPreviewExamples

public SealedClassesPreviewExamples()

Method Details

area

public double area(SealedClassesPreviewExamples.Shape shape)

Calculates the area of a known shape hierarchy.

Parameters:

shape - the shape to measure

Returns:

the shape area