java23種設(shè)計模式
在Java編程中，有23種常見的設(shè)計模式，它們被分為三個不同的分類：創(chuàng)建型模式（Creational Patterns）、結(jié)構(gòu)型模式（Structural Patterns）和行為型模式（Behavioral Patterns）。以下是對每種設(shè)計模式的簡要介紹以及示例代碼：
1. 創(chuàng)建型模式（Creational Patterns）：
??a. 單例模式（Singleton Pattern）：確保一個類只有一個實例，并提供全局訪問點。
```java
public class Singleton {
??private static Singleton instance;
??private Singleton() {
????// 私有構(gòu)造函數(shù)
??}
??public static Singleton getInstance() {
????if (instance == null) {
??????instance = new Singleton();
????}
????return instance;
??}
}
```
??b. 工廠模式（Factory Pattern）：通過使用工廠方法創(chuàng)建對象，而不直接實例化對象。
```java
public interface Shape {
??void draw();
}
public class Rectangle implements Shape {
??@Override
??public void draw() {
????System.out.println("Drawing a rectangle.");
??}
}
public class Circle implements Shape {
??@Override
??public void draw() {
????System.out.println("Drawing a circle.");
??}
}
public class ShapeFactory {
??public Shape createShape(String shapeType) {
????if (shapeType.equalsIgnoreCase("rectangle")) {
??????return new Rectangle();
????} else if (shapeType.equalsIgnoreCase("circle")) {
??????return new Circle();
????}
????return null;
??}
}
// 使用示例
ShapeFactory factory = new ShapeFactory();
Shape rectangle = factory.createShape("rectangle");
rectangle.draw();
Shape circle = factory.createShape("circle");
circle.draw();
```
??c. 抽象工廠模式（Abstract Factory Pattern）：提供一個接口，用于創(chuàng)建相關(guān)或依賴對象的家族，而無需指定具體類。
```java
public interface Shape {
??void draw();
}
public class Rectangle implements Shape {
??@Override
??public void draw() {
????System.out.println("Drawing a rectangle.");
??}
}
public class Circle implements Shape {
??@Override
??public void draw() {
????System.out.println("Drawing a circle.");
??}
}
public interface Color {
??void fill();
}
public class Red implements Color {
??@Override
??public void fill() {
????System.out.println("Filling with red color.");
??}
}
public class Blue implements Color {
??@Override
??public void fill() {
????System.out.println("Filling with blue color.");
??}
}
public interface AbstractFactory {
??Shape createShape();
??Color createColor();
}
public class ShapeFactory implements AbstractFactory {
??@Override
??public Shape createShape() {
????return new Rectangle();
??}
??@Override
??public Color createColor() {
????return new Red();
??}
}
public class ColorFactory implements AbstractFactory {
??@Override
??public Shape createShape() {
????return new Circle();
??}
??@Override
??public Color createColor() {
????return new Blue();
??}
}
// 使用示例
AbstractFactory shapeFactory = new ShapeFactory();
Shape shape = shapeFactory.createShape();
shape.draw();
Color color = shapeFactory.createColor();
color.fill();
AbstractFactory colorFactory = new ColorFactory();
Shape shape = colorFactory.createShape();
shape.draw();
Color color = colorFactory.createColor();
color.fill();
```
??d. 建造者模式（Builder Pattern）：將一個復雜對象的構(gòu)建與其表示分別，以便同樣的構(gòu)建過程可以創(chuàng)建不同的表示。
```java
public class Car {
??private String brand;
??private String model;
??private int year;
??private Car(Builder builder) {
????this.brand = builder.brand;
????this.model = builder.model;
????this.year = builder.year;
??}
??public String getBrand() {
????return brand;
??}
??public String getModel() {
????return model;
??}
??public int getYear() {
????return year;
??}
??public static class Builder {
????private String brand;
????private String model;
????private int year;
????public Builder setBrand(String brand) {
??????this.brand = brand;
??????return this;
????}
????public Builder setModel(String model) {
??????this.model = model;
??????return this;
????}
????public Builder setYear(int year) {
??????this.year = year;
??????return this;
????}
????public Car build() {
??????return new Car(this);
????}
??}
}
// 使用示例
Car car = new Car.Builder()
????.setBrand("Toyota")
????.setModel("Camry")
????.setYear(2022)
????.build();
System.out.println("Brand: " + car.getBrand());
System.out.println("Model: " + car.getModel());
System.out.println("Year: " + car.getYear());
```
2. 結(jié)構(gòu)型模式（Structural Patterns）：
??a. 適配器模式（Adapter Pattern）：將一個類的接口轉(zhuǎn)換成客戶端期望的另一個接口。
```java
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 {
??@Override
??public void playVlc(String fileName) {
????System.out.println("Playing vlc file: " + fileName);
??}
??@Override
??public void playMp4(String fileName) {
????// 空實現(xiàn)
??}
}
public class Mp4Player implements AdvancedMediaPlayer {
??@Override
??public void playVlc(String fileName) {
????// 空實現(xiàn)
??}
??@Override
??public void playMp4(String fileName) {
????System.out.println("Playing mp4 file: " + fileName);
??}
}
public class MediaAdapter implements MediaPlayer {
??private AdvancedMediaPlayer advancedMediaPlayer;
??public MediaAdapter(String audioType) {
????if (audioType.equalsIgnoreCase("vlc")) {
??????advancedMediaPlayer = new VlcPlayer();
????} else if (audioType.equalsIgnoreCase("mp4")) {
??????advancedMediaPlayer = new Mp4Player();
????}
??}
??@Override
??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 {
??private MediaAdapter mediaAdapter;
??@Override
??public void play(String audioType, String fileName) {
????if (audioType.equalsIgnoreCase("mp3")) {
??????System.out.println("Playing mp3 file: " + fileName);
????} else if (audioType.equalsIgnoreCase("vlc") || audioType.equalsIgnoreCase("mp4")) {
??????mediaAdapter = new MediaAdapter(audioType);
??????mediaAdapter.play(audioType, fileName);
????} else {
??????System.out.println("Invalid media type: " + audioType);
????}
??}
}
// 使用示例
MediaPlayer audioPlayer = new AudioPlayer();
audioPlayer.play("mp3", "song.mp3");
audioPlayer.play("vlc", "movie.vlc");
audioPlayer.play("mp4", "video.mp4");
audioPlayer.play("avi", "movie.avi");
```
b. 橋接模式（Bridge Pattern）：將抽象部分與其具體實現(xiàn)部分分離，使它們可以獨立變化。
```java
public interface Color {
??void applyColor();
}
public class Red implements Color {
??@Override
??public void applyColor() {
????System.out.println("Applying red color.");
??}
}
public class Blue implements Color {
??@Override
??public void applyColor() {
????System.out.println("Applying blue color.");
??}
}
public abstract class Shape {
??protected Color color;
??public Shape(Color color) {
????this.color = color;
??}
??abstract void applyColor();
}
public class Square extends Shape {
??public Square(Color color) {
????super(color);
??}
??@Override
??void applyColor() {
????System.out.print("Square ");
????color.applyColor();
??}
}
public class Circle extends Shape {
??public Circle(Color color) {
????super(color);
??}
??@Override
??void applyColor() {
????System.out.print("Circle ");
????color.applyColor();
??}
}
// 使用示例
Color redColor = new Red();
Shape square = new Square(redColor);
square.applyColor();
Color blueColor = new Blue();
Shape circle = new Circle(blueColor);
circle.applyColor();
```
3. 行為型模式（Behavioral Patterns）：
??a. 觀察者模式（Observer Pattern）：定義對象之間的一對多依賴關(guān)系，當一個對象狀態(tài)改變時，其所有依賴者都會收到通知并自動更新。
```java
import java.util.ArrayList;
import java.util.List;
public interface Observer {
??void update(String message);
}
public class User implements Observer {
??private String name;
??public User(String name) {
????this.name = name;
??}
??@Override
??public void update(String message) {
????System.out.println(name + " received a new message: " + message);
??}
}
public interface Subject {
??void attach(Observer observer);
??void detach(Observer observer);
??void notifyObservers(String message);
}
public class ChatRoom implements Subject {
??private List
