91 lines
1.9 KiB
Java
91 lines
1.9 KiB
Java
// patterns/ShapeFactory2.java
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// (c)2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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// Polymorphic factory methods
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import java.util.*;
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import java.util.function.*;
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import java.util.stream.*;
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class BadShapeCreation extends RuntimeException {
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BadShapeCreation(String msg) {
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super(msg);
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}
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}
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interface Shape {
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void draw();
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void erase();
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}
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abstract class ShapeFactory {
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static Map<String, Supplier<Shape>> factories =
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new HashMap<>();
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static Shape createShape(String id)
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throws BadShapeCreation {
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if(!factories.containsKey(id)) {
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try {
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Class.forName(id); // Load dynamically
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} catch(ClassNotFoundException e) {
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throw new BadShapeCreation(id);
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}
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// See if it was put in:
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if(!factories.containsKey(id))
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throw new BadShapeCreation(id);
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}
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return factories.get(id).get();
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}
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}
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class Circle implements Shape {
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private Circle() {}
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public void draw() {
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System.out.println("Circle.draw");
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}
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public void erase() {
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System.out.println("Circle.erase");
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}
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static {
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ShapeFactory.factories.put("Circle", Circle::new);
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}
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}
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class Square implements Shape {
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private Square() {}
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public void draw() {
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System.out.println("Square.draw");
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}
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public void erase() {
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System.out.println("Square.erase");
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}
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static {
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ShapeFactory.factories.put("Square", Square::new);
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}
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}
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public class ShapeFactory2 {
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public static void main(String[] args) {
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List<Shape> shapes = Stream.of("Circle", "Square",
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"Square", "Circle", "Circle", "Square")
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.map(ShapeFactory::createShape)
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.collect(Collectors.toList());
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shapes.forEach(Shape::draw);
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shapes.forEach(Shape::erase);
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}
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}
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/* Output:
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Circle.draw
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Square.draw
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Square.draw
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Circle.draw
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Circle.draw
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Square.draw
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Circle.erase
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Square.erase
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Square.erase
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Circle.erase
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Circle.erase
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Square.erase
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*/
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