Посетитель на Java

package refactoring_guru.visitor.example.shapes; import refactoring_guru.visitor.example.visitor.Visitor; public interface Shape { void move(int x, int y); void draw(); String accept(Visitor visitor); } 

package refactoring_guru.visitor.example.shapes; import refactoring_guru.visitor.example.visitor.Visitor; public class Dot implements Shape { private int id; private int x; private int y; public Dot() { } public Dot(int id, int x, int y) { this.id = id; this.x = x; this.y = y; } @Override public void move(int x, int y) { // move shape } @Override public void draw() { // draw shape } @Override public String accept(Visitor visitor) { return visitor.visitDot(this); } public int getX() { return x; } public int getY() { return y; } public int getId() { return id; } } 

package refactoring_guru.visitor.example.shapes; import refactoring_guru.visitor.example.visitor.Visitor; public class Circle extends Dot { private int radius; public Circle(int id, int x, int y, int radius) { super(id, x, y); this.radius = radius; } @Override public String accept(Visitor visitor) { return visitor.visitCircle(this); } public int getRadius() { return radius; } } 

package refactoring_guru.visitor.example.shapes; import refactoring_guru.visitor.example.visitor.Visitor; public class Rectangle implements Shape { private int id; private int x; private int y; private int width; private int height; public Rectangle(int id, int x, int y, int width, int height) { this.id = id; this.x = x; this.y = y; this.width = width; this.height = height; } @Override public String accept(Visitor visitor) { return visitor.visitRectangle(this); } @Override public void move(int x, int y) { // move shape } @Override public void draw() { // draw shape } public int getId() { return id; } public int getX() { return x; } public int getY() { return y; } public int getWidth() { return width; } public int getHeight() { return height; } } 

package refactoring_guru.visitor.example.shapes; import refactoring_guru.visitor.example.visitor.Visitor; import java.util.ArrayList; import java.util.List; public class CompoundShape implements Shape { public int id; public List<Shape> children = new ArrayList<>(); public CompoundShape(int id) { this.id = id; } @Override public void move(int x, int y) { // move shape } @Override public void draw() { // draw shape } public int getId() { return id; } @Override public String accept(Visitor visitor) { return visitor.visitCompoundGraphic(this); } public void add(Shape shape) { children.add(shape); } } 

package refactoring_guru.visitor.example.visitor; import refactoring_guru.visitor.example.shapes.Circle; import refactoring_guru.visitor.example.shapes.CompoundShape; import refactoring_guru.visitor.example.shapes.Dot; import refactoring_guru.visitor.example.shapes.Rectangle; public interface Visitor { String visitDot(Dot dot); String visitCircle(Circle circle); String visitRectangle(Rectangle rectangle); String visitCompoundGraphic(CompoundShape cg); } 

package refactoring_guru.visitor.example.visitor; import refactoring_guru.visitor.example.shapes.*; public class XMLExportVisitor implements Visitor { public String export(Shape... args) { StringBuilder sb = new StringBuilder(); sb.append("<?xml version=\"1.0\" encoding=\"utf-8\"?>" + "\n"); for (Shape shape : args) { sb.append(shape.accept(this)).append("\n"); } return sb.toString(); } public String visitDot(Dot d) { return "<dot>" + "\n" + " <id>" + d.getId() + "</id>" + "\n" + " <x>" + d.getX() + "</x>" + "\n" + " <y>" + d.getY() + "</y>" + "\n" + "</dot>"; } public String visitCircle(Circle c) { return "<circle>" + "\n" + " <id>" + c.getId() + "</id>" + "\n" + " <x>" + c.getX() + "</x>" + "\n" + " <y>" + c.getY() + "</y>" + "\n" + " <radius>" + c.getRadius() + "</radius>" + "\n" + "</circle>"; } public String visitRectangle(Rectangle r) { return "<rectangle>" + "\n" + " <id>" + r.getId() + "</id>" + "\n" + " <x>" + r.getX() + "</x>" + "\n" + " <y>" + r.getY() + "</y>" + "\n" + " <width>" + r.getWidth() + "</width>" + "\n" + " <height>" + r.getHeight() + "</height>" + "\n" + "</rectangle>"; } public String visitCompoundGraphic(CompoundShape cg) { return "<compound_graphic>" + "\n" + " <id>" + cg.getId() + "</id>" + "\n" + _visitCompoundGraphic(cg) + "</compound_graphic>"; } private String _visitCompoundGraphic(CompoundShape cg) { StringBuilder sb = new StringBuilder(); for (Shape shape : cg.children) { String obj = shape.accept(this); // Proper indentation for sub-objects. obj = " " + obj.replace("\n", "\n ") + "\n"; sb.append(obj); } return sb.toString(); } } 

package refactoring_guru.visitor.example; import refactoring_guru.visitor.example.shapes.*; import refactoring_guru.visitor.example.visitor.XMLExportVisitor; public class Demo { public static void main(String[] args) { Dot dot = new Dot(1, 10, 55); Circle circle = new Circle(2, 23, 15, 10); Rectangle rectangle = new Rectangle(3, 10, 17, 20, 30); CompoundShape compoundShape = new CompoundShape(4); compoundShape.add(dot); compoundShape.add(circle); compoundShape.add(rectangle); CompoundShape c = new CompoundShape(5); c.add(dot); compoundShape.add(c); export(circle, compoundShape); } private static void export(Shape... shapes) { XMLExportVisitor exportVisitor = new XMLExportVisitor(); System.out.println(exportVisitor.export(shapes)); } } 

<?xml version="1.0" encoding="utf-8"?> <circle> <id>2</id> <x>23</x> <y>15</y> <radius>10</radius> </circle> <?xml version="1.0" encoding="utf-8"?> <compound_graphic> <id>4</id> <dot> <id>1</id> <x>10</x> <y>55</y> </dot> <circle> <id>2</id> <x>23</x> <y>15</y> <radius>10</radius> </circle> <rectangle> <id>3</id> <x>10</x> <y>17</y> <width>20</width> <height>30</height> </rectangle> <compound_graphic> <id>5</id> <dot> <id>1</id> <x>10</x> <y>55</y> </dot> </compound_graphic> </compound_graphic>