在软件开发过程中，设计模式是一种解决特定问题的经验总结和最佳实践。设计模式可以被分为三大类：创建型模式、结构型模式、行为型模式。接下来我们将从不同的角度详细介绍这三大类设计模式。
一、创建型模式
创建型模式主要关注对象的创建过程，在对象的创建过程中封装复杂性，并提供灵活的方式创建对象。创建型模式包括以下几种模式：
1. 工厂方法模式
工厂方法模式定义一个用于创建对象的接口，让子类决定将哪一个类实例化。可以将需要创建的对象类型从具体工厂的实现中解耦出来，使得代码更加灵活。以下是工厂方法模式的示例代码：
interface Car {
void run();
}
class Benz implements Car {
@Override
public void run() {
System.out.println("Benz is running");
}
}
class BMW implements Car {
@Override
public void run() {
System.out.println("BMW is running");
}
}
interface CarFactory {
Car createCar();
}
class BenzFactory implements CarFactory {
@Override
public Car createCar() {
return new Benz();
}
}
class BMWFactory implements CarFactory {
@Override
public Car createCar() {
return new BMW();
}
}
public class Main {
public static void main(String[] args) {
CarFactory factory = new BenzFactory();
Car car = factory.createCar();
car.run();
}
}
2. 抽象工厂模式
抽象工厂模式提供一个用于创建一系列相关或相互依赖对象的接口，而无需指定它们具体的类。抽象工厂可以为用户提供一组对象，这组对象的实现可以有多种选择，基于用户的需求而变化。以下是抽象工厂模式的示例代码：
interface Engine {
void start();
}
interface Wheel {
void roll();
}
interface CarFactory {
Engine createEngine();
Wheel createWheel();
}
class BenzEngine implements Engine {
@Override
public void start() {
System.out.println("Benz engine start");
}
}
class BMWEngine implements Engine {
@Override
public void start() {
System.out.println("BMW engine start");
}
}
class BenzWheel implements Wheel {
@Override
public void roll() {
System.out.println("Benz wheel roll");
}
}
class BMWWheel implements Wheel {
@Override
public void roll() {
System.out.println("BMW wheel roll");
}
}
class BenzFactory implements CarFactory {
@Override
public Engine createEngine() {
return new BenzEngine();
}
@Override
public Wheel createWheel() {
return new BenzWheel();
}
}
class BMWFactory implements CarFactory {
@Override
public Engine createEngine() {
return new BMWEngine();
}
@Override
public Wheel createWheel() {
return new BMWWheel();
}
}
public class Main {
public static void main(String[] args) {
CarFactory factory = new BenzFactory();
Engine engine = factory.createEngine();
Wheel wheel = factory.createWheel();
engine.start();
wheel.roll();
}
}
二、结构型模式
结构型模式主要关注对象的组合方式，通过对象间的类组合形成更大的结构，使得系统更加灵活和易于维护。结构型模式包括以下几种模式：
1. 适配器模式
适配器模式将一个类的接口转换为客户希望的另外一个接口，适配器模式可以让原本不兼容的类在一起工作。以下是适配器模式的示例代码：
interface Electronic220V {
void powerOn();
}
class Outlet {
public void powerOn(Electronic220V electronic220V) {
electronic220V.powerOn();
}
}
class Electronic110V {
public void powerOn() {
System.out.println("Electronic110V is powered on");
}
}
class ElectronicAdapter implements Electronic220V {
private Electronic110V electronic110V;
public ElectronicAdapter(Electronic110V electronic110V) {
this.electronic110V = electronic110V;
}
@Override
public void powerOn() {
electronic110V.powerOn();
}
}
public class Main {
public static void main(String[] args) {
Electronic110V electronic110V = new Electronic110V();
ElectronicAdapter adapter = new ElectronicAdapter(electronic110V);
Outlet outlet = new Outlet();
outlet.powerOn(adapter);
}
}
2. 装饰器模式
装饰器模式可以动态地给一个对象添加一些额外的职责，同时又不改变其结构。装饰器模式可以实现设计要求开放闭合原则（Open–Closed Principle），即软件实体应该对扩展开放，对修改关闭。以下是装饰器模式的示例代码：
interface Shape {
void draw();
}
class Circle implements Shape {
@Override
public void draw() {
System.out.println("Draw a circle");
}
}
class Square implements Shape {
@Override
public void draw() {
System.out.println("Draw a square");
}
}
abstract class ShapeDecorator implements Shape {
protected Shape decoratedShape;
public ShapeDecorator(Shape decoratedShape) {
this.decoratedShape = decoratedShape;
}
@Override
public void draw() {
decoratedShape.draw();
}
}
class RedBorderDecorator extends ShapeDecorator {
public RedBorderDecorator(Shape decoratedShape) {
super(decoratedShape);
}
@Override
public void draw() {
decoratedShape.draw();
System.out.println("Add a red border");
}
}
public class Main {
public static void main(String[] args) {
Shape circle = new Circle();
Shape redCircle = new RedBorderDecorator(circle);
Shape redSquare = new RedBorderDecorator(new Square());
circle.draw();
redCircle.draw();
redSquare.draw();
}
}
三、行为型模式
行为型模式主要关注对象间的通信方式和通信协议，通过定义对象间的交互进行协同工作，从而完成特定的功能。行为型模式包括以下几种模式：
1. 观察者模式
观察者模式定义了一个一对多的依赖关系，当对象状态发生改变时，所有依赖它的对象都会收到通知并自动更新。以下是观察者模式的示例代码：
import java.util.ArrayList;
import java.util.List;
interface Observer {
void update();
}
class Subject {
private List observers = new ArrayList();
public void attach(Observer observer) {
observers.add(observer);
}
public void detach(Observer observer) {
observers.remove(observer);
}
public void notifyObservers() {
for (Observer observer : observers) {
observer.update();
}
}
}
class ConcreteObserver implements Observer {
private String name;
private Subject subject;
public ConcreteObserver(String name, Subject subject) {
this.name = name;
this.subject = subject;
}
@Override
public void update() {
System.out.println(name + " received notification");
}
}
public class Main {
public static void main(String[] args) {
Subject subject = new Subject();
Observer observer1 = new ConcreteObserver("Observer1", subject);
Observer observer2 = new ConcreteObserver("Observer2", subject);
Observer observer3 = new ConcreteObserver("Observer3", subject);
subject.attach(observer1);
subject.attach(observer2);
subject.attach(observer3);
subject.notifyObservers();
}
}
2. 命令模式
命令模式将请求封装成对象，以便解耦发送者和接收者。命令模式中包含的对象有：请求者、接收者、命令对象和客户端。以下是命令模式的示例代码：
interface Command {
void execute();
}
class Receiver {
public void action() {
System.out.println("Action");
}
}
class ConcreteCommand implements Command {
private Receiver receiver;
public ConcreteCommand(Receiver receiver) {
this.receiver = receiver;
}
@Override
public void execute() {
receiver.action();
}
}
class Invoker {
private Command command;
public void setCommand(Command command) {
this.command = command;
}
public void executeCommand() {
command.execute();
}
}
public class Main {
public static void main(String[] args) {
Receiver receiver = new Receiver();
ConcreteCommand command = new ConcreteCommand(receiver);
Invoker invoker = new Invoker();
invoker.setCommand(command);
invoker.executeCommand();
}
}
以上就是对设计模式分为哪三大类的讲解，通过示例代码加深了对每个模式的具体理解，希望对读者有所帮助。
原创文章，作者：ETIMX，如若转载，请注明出处：https://www.506064.com/n/349414.html
微信扫一扫 
支付宝扫一扫 