java设计模式 代码
时间: 2023-11-12 21:45:53 浏览: 38
当谈到Java设计模式,有许多经典的模式可以应用在不同的场景中。以下是几个常见的设计模式以及对应的代码示例:
1. 单例模式(Singleton Pattern):
```java
public class Singleton {
private static Singleton instance;
private Singleton() {}
public static Singleton getInstance() {
if (instance == null) {
instance = new Singleton();
}
return instance;
}
}
```
2. 工厂模式(Factory Pattern):
```java
public interface Shape {
void draw();
}
public class Rectangle implements Shape {
@Override
public void draw() {
System.out.println("Inside Rectangle::draw() method.");
}
}
public class Circle implements Shape {
@Override
public void draw() {
System.out.println("Inside Circle::draw() method.");
}
}
public class ShapeFactory {
public Shape getShape(String shapeType) {
if (shapeType.equalsIgnoreCase("RECTANGLE")) {
return new Rectangle();
} else if (shapeType.equalsIgnoreCase("CIRCLE")) {
return new Circle();
}
return null;
}
}
```
3. 观察者模式(Observer Pattern):
```java
import java.util.ArrayList;
import java.util.List;
public interface Observer {
void update(String message);
}
public class ConcreteObserver implements Observer {
private String name;
public ConcreteObserver(String name) {
this.name = name;
}
@Override
public void update(String message) {
System.out.println(name + " received message: " + message);
}
}
public interface Subject {
void registerObserver(Observer observer);
void removeObserver(Observer observer);
void notifyObservers(String message);
}
public class ConcreteSubject implements Subject {
private List<Observer> observers = new ArrayList<>();
@Override
public void registerObserver(Observer observer) {
observers.add(observer);
}
@Override
public void removeObserver(Observer observer) {
observers.remove(observer);
}
@Override
public void notifyObservers(String message) {
for (Observer observer : observers) {
observer.update(message);
}
}
}
```
这些只是一些常见的设计模式和相应的代码示例,Java设计模式有很多种类,每个模式都有自己特定的应用场景。希望这些示例能为你提供一些帮助!