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<!DOCTYPE HTML>
<html lang="zh-CN">
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public class Singleton {
private Singleton(){}
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<div id="loading-container">
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<h1 id="单例模式"><a href="#单例模式" class="headerlink" title="单例模式"></a>单例模式</h1><h2 id="懒汉模式"><a href="#懒汉模式" class="headerlink" title="懒汉模式"></a>懒汉模式</h2><p>为了线程安全</p>
<pre><code>public class Singleton {
private Singleton(){}
private volatile static Singleton instance;
public Singleton getInstance(){
if (instance==null){
synchronized (Singleton.class){
if (instance==null){
instance=new Singleton();
}
}
}
return instance;
}
}</code></pre><h2 id="饿汉模式"><a href="#饿汉模式" class="headerlink" title="饿汉模式"></a>饿汉模式</h2><pre><code>public class Singleton {
private volatile static Singleton instance=new Singleton();
public static Singleton getInstance() {
return instance;
}
}
</code></pre><h1 id="工厂模式"><a href="#工厂模式" class="headerlink" title="工厂模式"></a>工厂模式</h1><h2 id="简单模式"><a href="#简单模式" class="headerlink" title="简单模式"></a>简单模式</h2><p>增加新产品时还是需要修改工厂类的代码，违背了“开闭原则”。</p>
<pre><code>// 定义一个形状接口
public interface Shape {
void draw();
}
// 定义一个圆形类，实现形状接口
public class Circle implements Shape {
@Override
public void draw() {
System.out.println("Inside Circle::draw() method.");
}
}
// 定义一个矩形类，实现形状接口
public class Rectangle implements Shape {
@Override
public void draw() {
System.out.println("Inside Rectangle::draw() method.");
}
}
// 定义一个正方形类，实现形状接口
public class Square implements Shape {
@Override
public void draw() {
System.out.println("Inside Square::draw() method.");
}
}
// 定义一个形状工厂类，根据参数返回相应的形状对象
public class ShapeFactory {
// 使用 getShape 方法获取形状类型的对象
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();
} else if (shapeType.equalsIgnoreCase("SQUARE")) {
return new Square();
}
return null;
}
}
// 定义一个测试类，用来测试工厂模式的功能
public class FactoryPatternDemo {
public static void main(String[] args) {
// 创建一个形状工厂对象
ShapeFactory shapeFactory = new ShapeFactory();
// 获取 Circle 的对象，并调用它的 draw 方法
Shape shape1 = shapeFactory.getShape("CIRCLE");
// 调用 Circle 的 draw 方法
shape1.draw();
// 获取 Rectangle 的对象，并调用它的 draw 方法
Shape shape2 = shapeFactory.getShape("RECTANGLE");
// 调用 Rectangle 的 draw 方法
shape2.draw();
// 获取 Square 的对象，并调用它的 draw 方法
Shape shape3 = shapeFactory.getShape("SQUARE");
// 调用 Square 的 draw 方法
shape3.draw();
}
}
</code></pre><h2 id="工厂方法模式"><a href="#工厂方法模式" class="headerlink" title="工厂方法模式"></a>工厂方法模式</h2><p>每增加一个产品就要增加一个具体产品类和一个对应的具体工厂类，这增加了系统的复杂度。</p>
<pre><code>// 抽象产品
interface Product {
void produce();
}
// 具体产品A
class ConcreteProductA implements Product {
@Override
public void produce() {
System.out.println("Product A produced.");
}
}
// 具体产品B
class ConcreteProductB implements Product {
@Override
public void produce() {
System.out.println("Product B produced.");
}
}
// 抽象工厂
interface Factory {
Product createProduct();
}
// 具体工厂A
class ConcreteFactoryA implements Factory {
@Override
public Product createProduct() {
return new ConcreteProductA();
}
}
// 具体工厂B
class ConcreteFactoryB implements Factory {
@Override
public Product createProduct() {
return new ConcreteProductB();
}
}
// 客户端
public class FactoryMethodPatternExample {
public static void main(String[] args) {
Factory factoryA = new ConcreteFactoryA();
Product productA = factoryA.createProduct();
productA.produce(); // Output: Product A produced.
Factory factoryB = new ConcreteFactoryB();
Product productB = factoryB.createProduct();
productB.produce(); // Output: Product B produced.
}
}
</code></pre><h2 id="抽象工厂模式"><a href="#抽象工厂模式" class="headerlink" title="抽象工厂模式"></a>抽象工厂模式</h2><ul>
<li>抽象工厂（Abstract Factory）：定义了一个用于创建一族产品对象的接口，每个方法对应一种产品类型。</li>
<li>具体工厂（Concrete Factory）：实现了抽象工厂接口，负责创建具体的产品对象。</li>
<li>抽象产品（Abstract Product）：定义了一组产品对象的公共接口，描述了产品对象的公共方法。</li>
<li>具体产品（Concrete Product）：实现了抽象产品接口，定义了具体产品的特定行为和属性。</li>
</ul>
<pre><code>// 定义一个形状接口
public interface Shape {
void draw();
}
// 定义一个圆形类，实现形状接口
public class Circle implements Shape {
@Override
public void draw() {
System.out.println("Inside Circle::draw() method.");
}
}
// 定义一个矩形类，实现形状接口
public class Rectangle implements Shape {
@Override
public void draw() {
System.out.println("Inside Rectangle::draw() method.");
}
}
// 定义一个正方形类，实现形状接口
public class Square implements Shape {
@Override
public void draw() {
System.out.println("Inside Square::draw() method.");
}
}
// 定义一个颜色接口
public interface Color {
void fill();
}
// 定义一个红色类，实现颜色接口
public class Red implements Color {
@Override
public void fill() {
System.out.println("Inside Red::fill() method.");
}
}
// 定义一个绿色类，实现颜色接口
public class Green implements Color {
@Override
public void fill() {
System.out.println("Inside Green::fill() method.");
}
}
// 定义一个蓝色类，实现颜色接口
public class Blue implements Color {
@Override
public void fill() {
System.out.println("Inside Blue::fill() method.");
}
}
// 定义一个抽象工厂类，声明了两个用于创建形状和颜色对象的方法