定义一个用于创建对象的接口，让子类决定实例化哪一个类。工厂方法使一个类的实例化延迟到子类。
在简单工厂中，创建对象的是简单工厂类；而在工厂方法中，创建对象的是继承了父类工厂的子类。
类图
实现
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| public interface Product {
}
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| public class ConcreteProduct1 implements Product {
}
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| public class ConcreteProduct2 implements Product {
}
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| public abstract class Factory {
public abstract Product factoryMethod();
}
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| public class ConcreteFactory1 extends Factory {
@Override
public Product factoryMethod() {
return new ConcreteProduct1();
}
}
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| public class ConcreteFactory2 extends Factory {
@Override
public Product factoryMethod() {
return new ConcreteProduct2();
}
}
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| public class Client {
public static void main(String[] args) {
Factory factory = new ConcreteFactory1();
Product product = factory.factoryMethod();
}
}
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