java - Java 问题中的工厂方法模式示例

Question

我正在尝试用 Java 创建一个非常简单的工厂方法设计模式示例。我不太了解 Java，一般来说我是编程新手，但我需要想出一个用 Java 实现的基本 FactoryMethod 示例。以下是我想出的。我确定有很多错误，我显然缺少一些构造函数，而且我对抽象类和接口(interface)感到困惑。你能指出我的错误并更正我的代码并附上解释吗？预先感谢您的时间和帮助。

public abstract class Person 
{   
    public void createPerson(){ }
}

public class Male extends Person 
{   
    @Override
    public void createPerson() 
    {
        System.out.print("a man has been created");
    }
}

public class Female extends Person 
{   
    @Override
    public void createPerson() 
    {
        System.out.print("a woman has been created");
    }
}

public class PersonFactory
{
     public static Person makePerson(String x) // I have no Person constructor in
     {                                         // the actual abstract person class so 
         if(x=="male")                         // is this valid here?
         { 
             Male man=new Male();
             return man;
          }
          else
         {
             Female woman=new Female();
             return woman;
         }
     }
}


public class Test 
{
    public static void main(String[] args)
    {
       Person y= new Person(makePerson("male"));   // definitely doing smth wrong here
       Person z= new Person(makePerson("female")); // yup, here as well
    }
}

Answer 1

简而言之，您的版本中有几个问题已在下面更正:

1. createPerson 方法没用。
2. 你调用工厂方法的方式是错误的。
3. 您在工厂方法中使用 == 而不是 .equals。

我增强了您的 Person 类以添加由 Male 和 Female 类共享的成员字段，以演示如何使用共享公共(public)抽象构造函数。

public abstract class Person {   
    protected final String name;
    public Person(String name) { 
        this.name = name;
    }
}

public class Male extends Person {
    public Male(String name) { 
        super(name);
    }
}

public class Female extends Person {
    public Female(String name) { 
        super(name);
    }
}

public class PersonFactory
{
     public static Person makePerson(String gender, String name) 
     {
         if(gender.equals("male"))                       
         { 
             Male man=new Male(name);
             return man;
         }
         else
         {
             Female woman=new Female(name);
             return woman;
         }
     }
}

public class Test 
{
    public static void main(String[] args)
    {
       Person y= PersonFactory.makePerson("male", "bob"));
       Person z= new PersonFactory.makePerson("female", "janet"));
    }
}