/**
 * 工厂方法
 */
public interface IFactory {
    LeiFeng createLeiFeng();
}

/**
 * 雷锋
 */
public class LeiFeng {
    public void sweep() {
        System.out.println("扫地");
    }

    public void wash() {
        System.out.println("洗衣");
    }

    public void buyRice() {
        System.out.println("买米");
    }

}

/**
 * 学雷锋的大学生
 */
public class Undergraduate extends LeiFeng {
}


/**
 * 工厂方法生成学雷锋的大学生
 */
public class UndergraduateFactory implements IFactory {
    @Override
    public LeiFeng createLeiFeng() {
        return new Undergraduate();
    }
}

/**
 * 学雷锋的社区志愿者
 */
public class Volunteer extends LeiFeng {
}


/**
 * 工厂方法生成学雷锋的社区志愿者
 */
public class VolunteerFactory implements IFactory {
    @Override
    public LeiFeng createLeiFeng() {
        return new Volunteer();
    }
}

如果使用简单工厂实现：

/**
 * 简单工厂
 */
public class SimpleFactory {
    public static LeiFeng createLeiFeng(String type) {
        LeiFeng result = null;
        switch (type) {
            case "学雷锋的大学生":
                result = new Undergraduate();
                break;
            case "社区志愿者":
                result = new Undergraduate();
                break;
        }
        return result;
    }
}

Main：

public class Main {
    public static void main(String[] args) {
//        简单工厂实现
        LeiFeng student1 = SimpleFactory.createLeiFeng("学雷锋的大学生");
        student1.sweep();
//        工厂方法实现
        IFactory factory = new UndergraduateFactory();
        LeiFeng student2 = factory.createLeiFeng();
        student2.sweep();
    }
}