Comprendre les modèles de conception Java : introduction à 7 modèles de conception couramment utilisés, des exemples de code spécifiques sont requis
Les modèles de conception Java sont une solution universelle aux problèmes de conception de logiciels. Ils fournissent un ensemble d'idées de conception et de code de conduite largement acceptés. Les modèles de conception nous aident à mieux organiser et planifier la structure du code, rendant le code plus maintenable, lisible et évolutif. Dans cet article, nous présenterons 7 modèles de conception couramment utilisés en Java et fournirons des exemples de code correspondants.
public class Singleton { private static Singleton instance; private Singleton() { // 私有构造函数,防止外部实例化 } public static Singleton getInstance() { if (instance == null) { synchronized (Singleton.class) { if (instance == null) { instance = new Singleton(); } } } return instance; } }
public interface Shape { void draw(); } public class Circle implements Shape { @Override public void draw() { System.out.println("Circle::draw()"); } } public class Rectangle implements Shape { @Override public void draw() { System.out.println("Rectangle::draw()"); } } public class ShapeFactory { public Shape getShape(String shapeType) { if (shapeType == null) { return null; } if (shapeType.equalsIgnoreCase("CIRCLE")) { return new Circle(); } else if (shapeType.equalsIgnoreCase("RECTANGLE")) { return new Rectangle(); } return null; } }
import java.util.ArrayList; import java.util.List; public class Subject { private List<Observer> observers = new ArrayList<>(); private int state; public int getState() { return state; } public void setState(int state) { this.state = state; notifyAllObservers(); } public void attach(Observer observer) { observers.add(observer); } public void notifyAllObservers() { for (Observer observer : observers) { observer.update(); } } } public abstract class Observer { protected Subject subject; public abstract void update(); } public class BinaryObserver extends Observer { public BinaryObserver(Subject subject) { this.subject = subject; this.subject.attach(this); } public void update() { System.out.println("Binary String: " + Integer.toBinaryString(subject.getState())); } } public class OctalObserver extends Observer { public OctalObserver(Subject subject) { this.subject = subject; this.subject.attach(this); } public void update() { System.out.println("Octal String: " + Integer.toOctalString(subject.getState())); } } public class HexObserver extends Observer { public HexObserver(Subject subject) { this.subject = subject; this.subject.attach(this); } public void update() { System.out.println("Hex String: " + Integer.toHexString(subject.getState())); } } public class ObserverPatternDemo { public static void main(String[] args) { Subject subject = new Subject(); new BinaryObserver(subject); new OctalObserver(subject); new HexObserver(subject); System.out.println("First state change: 15"); subject.setState(15); System.out.println("Second state change: 10"); subject.setState(10); } }
public class Computer { private String cpu; private String memory; private String disk; // 省略其他属性和方法 } public interface ComputerBuilder { ComputerBuilder setCpu(String cpu); ComputerBuilder setMemory(String memory); ComputerBuilder setDisk(String disk); Computer build(); } public class BasicComputerBuilder implements ComputerBuilder { private Computer computer; public BasicComputerBuilder() { computer = new Computer(); } public ComputerBuilder setCpu(String cpu) { computer.setCpu(cpu); return this; } public ComputerBuilder setMemory(String memory) { computer.setMemory(memory); return this; } public ComputerBuilder setDisk(String disk) { computer.setDisk(disk); return this; } public Computer build() { return computer; } } public class Director { private ComputerBuilder computerBuilder; public Director(ComputerBuilder computerBuilder) { this.computerBuilder = computerBuilder; } public Computer construct() { return computerBuilder .setCpu("i5") .setMemory("8GB") .setDisk("1TB") .build(); } } public class BuilderPatternDemo { public static void main(String[] args) { ComputerBuilder computerBuilder = new BasicComputerBuilder(); Director director = new Director(computerBuilder); Computer computer = director.construct(); System.out.println(computer.toString()); } }
public abstract class Shape implements Cloneable { private String id; protected String type; abstract void draw(); public String getId() { return id; } public void setId(String id) { this.id = id; } public Object clone() { Object clone = null; try { clone = super.clone(); } catch (CloneNotSupportedException e) { e.printStackTrace(); } return clone; } } public class Circle extends Shape { public Circle() { type = "Circle"; } public void draw() { System.out.println("Inside Circle::draw() method."); } } public class Rectangle extends Shape { public Rectangle() { type = "Rectangle"; } public void draw() { System.out.println("Inside Rectangle::draw() method."); } } public class ShapeCache { private static Map<String, Shape> shapeMap = new HashMap<>(); public static Shape getShape(String shapeId) { Shape cachedShape = shapeMap.get(shapeId); return (Shape) cachedShape.clone(); } public static void loadCache() { Circle circle = new Circle(); circle.setId("1"); shapeMap.put(circle.getId(), circle); Rectangle rectangle = new Rectangle(); rectangle.setId("2"); shapeMap.put(rectangle.getId(), rectangle); } } public class PrototypePatternDemo { public static void main(String[] args) { ShapeCache.loadCache(); Shape clonedShape1 = ShapeCache.getShape("1"); System.out.println("Shape: " + clonedShape1.getType()); Shape clonedShape2 = ShapeCache.getShape("2"); System.out.println("Shape: " + clonedShape2.getType()); } }
public interface MediaPlayer { void play(String audioType, String fileName); } public interface AdvancedMediaPlayer { void playVlc(String fileName); void playMp4(String fileName); } public class VlcPlayer implements AdvancedMediaPlayer { public void playVlc(String fileName) { System.out.println("Playing vlc file. Name: " + fileName); } public void playMp4(String fileName) { // 空实现 } } public class Mp4Player implements AdvancedMediaPlayer { public void playVlc(String fileName) { // 空实现 } public void playMp4(String fileName) { System.out.println("Playing mp4 file. Name: " + fileName); } } public class MediaAdapter implements MediaPlayer { AdvancedMediaPlayer advancedMediaPlayer; public MediaAdapter(String audioType) { if (audioType.equalsIgnoreCase("vlc")) { advancedMediaPlayer = new VlcPlayer(); } else if (audioType.equalsIgnoreCase("mp4")) { advancedMediaPlayer = new Mp4Player(); } } public void play(String audioType, String fileName) { if (audioType.equalsIgnoreCase("vlc")) { advancedMediaPlayer.playVlc(fileName); } else if (audioType.equalsIgnoreCase("mp4")) { advancedMediaPlayer.playMp4(fileName); } } } public class AudioPlayer implements MediaPlayer { MediaAdapter mediaAdapter; public void play(String audioType, String fileName) { if (audioType.equalsIgnoreCase("mp3")) { System.out.println("Playing mp3 file. Name: " + fileName); } else if (audioType.equalsIgnoreCase("vlc") || audioType.equalsIgnoreCase("mp4")) { mediaAdapter = new MediaAdapter(audioType); mediaAdapter.play(audioType, fileName); } else { System.out.println("Invalid media. " + audioType + " format not supported"); } } } public class AdapterPatternDemo { public static void main(String[] args) { AudioPlayer audioPlayer = new AudioPlayer(); audioPlayer.play("mp3", "beyond_the_horizon.mp3"); audioPlayer.play("mp4", "alone.mp4"); audioPlayer.play("vlc", "far_far_away.vlc"); audioPlayer.play("avi", "mind_me.avi"); } }
public interface Strategy { int doOperation(int num1, int num2); } public class OperationAdd implements Strategy { public int doOperation(int num1, int num2) { return num1 + num2; } } public class OperationSubtract implements Strategy { public int doOperation(int num1, int num2) { return num1 - num2; } } public class OperationMultiply implements Strategy { public int doOperation(int num1, int num2) { return num1 * num2; } } public class Context { private Strategy strategy; public Context(Strategy strategy) { this.strategy = strategy; } public int executeStrategy(int num1, int num2) { return strategy.doOperation(num1, num2); } } public class StrategyPatternDemo { public static void main(String[] args) { Context context = new Context(new OperationAdd()); System.out.println("10 + 5 = " + context.executeStrategy(10, 5)); context = new Context(new OperationSubtract()); System.out.println("10 - 5 = " + context.executeStrategy(10, 5)); context = new Context(new OperationMultiply()); System.out.println("10 * 5 = " + context.executeStrategy(10, 5)); } }
Grâce à l'exemple de code ci-dessus, nous avons une brève introduction aux 7 modèles de conception couramment utilisés en Java. Chaque modèle de conception comporte différents scénarios et applications, et ils peuvent entrer en jeu dans différents projets. J'espère que cet article pourra vous aider à comprendre et à appliquer des modèles de conception, ainsi qu'à améliorer la qualité de votre code et l'efficacité de votre développement.
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