Class SealedClassesExamples

java.lang.Object

net.jrodolfo.java_evolution.java17.SealedClassesExamples

public class SealedClassesExamples
extends Object

Demonstrates sealed classes, finalized in Java 17.

Before sealed classes, Java could not directly express a closed hierarchy in the type system. A parent type was usually open to any accessible subtype, even when the domain had a known finite set of valid implementations.

A sealed type solves this by explicitly controlling which classes or interfaces may implement or extend it. This makes domain hierarchies easier to understand and safer to exhaustively handle.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final record	SealedClassesExamples.Circle	Final permitted implementation.
static final record	SealedClassesExamples.Rectangle	Final permitted implementation.
static interface	SealedClassesExamples.Shape	Sealed parent interface that permits only the listed implementations.
static class	SealedClassesExamples.Square	Non-sealed implementation, showing that a permitted subtype may reopen the hierarchy.

Constructor Summary

Constructors

Constructor	Description
SealedClassesExamples()

Method Summary

Modifier and Type	Method	Description
double	area(SealedClassesExamples.Shape shape)	Calculates the area for a known sealed shape hierarchy.

Methods inherited from class Object

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

Constructor Details

SealedClassesExamples

public SealedClassesExamples()

Method Details

area

public double area(SealedClassesExamples.Shape shape)

Calculates the area for a known sealed shape hierarchy.

Parameters:

shape - the shape to measure

Returns:

the calculated area