我的建议是使用比较器.请参阅下面的类的草图.

import java.util.HashMap;

import java.util.Map;

public abstract class Calculator {

public static Map weights;

static {

weights = new HashMap();

weights.put("price", 10);

weights.put("gender", 2);

weights.put("geo", 5);

}

public abstract int calculate(Map request);

public abstract int fitnessFor(Map request);

}

您可以使用权重来调整各个请求参数的相对重要性.

import java.util.Map;

public class Calculator1 extends Calculator {

public int calculate(Map request) {

return -1;

}

@Override

public int fitnessFor(Map request) {

int fitness = -1;

Integer price = request.get("price");

if (price == null)

return fitness;

if (price > 10)

fitness += weights.get("price");

return fitness;

}

public String toString() { return "Calculator1"; }

}

Calculator1只在乎昂贵的物品.

import java.util.Map;

public class Calculator2 extends Calculator {

public int calculate(Map request) {

return -1;

}

@Override

public int fitnessFor(Map request) {

int fitness = -1;

Integer price = request.get("price");

if (price == null)

return fitness;

if (price < 5)

fitness += weights.get("price");

Integer gender = request.get("gender");

if (gender == null)

return fitness;

if (gender == 1)

fitness += weights.get("gender");

return fitness;

}

public String toString() { return "Calculator2"; }

}

Calculator2在乎价格较低的物品,尤其是.如果他们是性别1.

比较器仅根据计算器相对于请求的适用性来比较计算器：

import java.util.Comparator;

import java.util.Map;

public class CalcComparator implements Comparator {

private Map request;

public CalcComparator(Map request) {

this.request = request;

}

@Override

public int compare(Calculator c1, Calculator c2) {

int c1Fitness = c1.fitnessFor(request);

int c2Fitness = c2.fitnessFor(request);

if (c1Fitness == c2Fitness)

return 0;

if (c1Fitness < c2Fitness)

return 1;

return -1;

}

}

试试看：

public class Main {

public static void main(String[] args) {

Map request = new HashMap();

request.put("price", 5);

request.put("gender", 1);

List calculators = new ArrayList();

calculators.add(new Calculator1());

calculators.add(new Calculator2());

Collections.sort(calculators, new CalcComparator(request));

System.out.println("For request: "+request);

for (Calculator c : calculators) {

System.out.println(""+c.toString() + "( fitness " + c.fitnessFor(request) + ")");

}

}

}

这只是一个草图来说明这个想法.您可能会想为请求参数引入一个枚举,可能会引入一个Request类,最有可能完全改变适应度的计算方式,将某些字段设为私有并封装它们,等等.

好处是,您可以根据它们对请求的适用性轻松获得所有计算器的订购.