// producer.java

import java.util.ArrayList;

public interface Producer{

      ArrayList<Integer> produce(int length);

}

// modelbase.java

abstract public classModelBase{

}

// model.java

import java.util.ArrayList;

class Model extends ModelBase{

    private Producer producer;

    void setProducer(Producer producer){

        this.producer = producer;

    }

    ArrayList<Integer> test(int length){

        return this.producer.producer(length);

    }

}

1.  編寫FibonacciProducer類，實現斐波那契數列

示例：

    Model model = new Model();

    model.setProducer(new FibonacciProducer());

    System.out.print(model.test(10));

輸出    [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]

2. 給model和producer的建立提供一些額外的自由度，編寫ModelFactory類和ProducerFactory類

示例：

    Model model = ModelFactory.create();

    model.setProducer(ProducerFactory.create('fibonacci'));

    System.out.print(model.test(10));

輸出    [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]

這個面試題挺有意思的，所以我想儲存一下，在面試的時候沒想這麼多，回家了以後，慢慢品味，感覺還是挺有意思的。下面開始實現。

1.

class FibonacciProducer implements Producer{
    static int a = 0;
    static int b = 1;
    static int c = 0;
    @Override
    public ArrayList<Integer> produce(int length) {
        ArrayList<Integer> list = new ArrayList<>();
        for (int i = 0; i < length; i++) {
            list.add(ret(i));
        }
        return list;
    }

    public static int ret(int value){
        if( value < 2 ){
            a = b;
            return 1;
        } else {
            c = a + b;
            a = b;
            b = c;
            return c;
        }
    }
}

2.

class ModelFactory{
    public static ModelBase create(){
        return new Model();
    }
}

class ProducerFactory{
    public static Producer create(String name){
        if(name != null && name.equals("fibonacci")){
            return new FibonacciProducer();
        }
        return null;
    }
}