如何制作一个通用的ValueComparator来对多个HashMap进行排序

Question

我第一次开始使用单个HashMap，例如：

private static Map<Broker, Integer> brokerSalesCountList = new HashMap<Broker, Integer>();

并使用

private static ValueComparator4Broker bvc =  new ValueComparator4Broker(brokerSalesCountList);
private static TreeMap<Broker,Integer> sortedbrokerSalesCountList  = new TreeMap<Broker,Integer>(bvc);
sortedbrokerSalesCountList.putAll(brokerSalesCountList);

这是我的值比较器代码：

public class ValueComparator4Broker implements Comparator<Broker> {
    Map<Broker, Integer> base;
    public ValueComparator4Broker(Map<Broker, Integer> base) {
        this.base = base;
    }
    @Override
    public int compare(Broker a, Broker b) {
        if (base.get(a) >= base.get(b)) {
            return -1;
        } else {
            return 1;
        }
    }
}

问题：现在我有两个以上的新哈希映射要以相同的方式排序，并且我不想复制ValueComparator4Broker类的代码，而是想创建一个通用的参数化ValueComparator，它可以被所有新的*HashMap*s:使用

private static Map<Area, Integer> areaBrokerCountList = new HashMap<Area, Integer>();
private static Map<Area, Integer> areaSalesTotalList = new HashMap<Area, Integer>();

我尝试了如下操作，但代码是错误的，甚至不接受用HashMap的键对象来代替Type。任何对改进方法和代码示例的帮助都将不胜感激：

import java.lang.reflect.Type;
import java.util.Comparator;
import java.util.Map;
public class ValueComparator implements Comparator<Type> {  
    Map<Type, Integer> base;
    public ValueComparator(Map<Type, Integer> base) {
        this.base = base;
    }
    @Override
    public int compare(Type a, Type b) {
        if (base.get(a) >= base.get(b)) {
            return -1;
        } else {
            return 1;
        } // returning 0 would merge keys
    }
}

Answer 1

我不太擅长冷输入泛型代码，但我的想法是：

这样使用类：

Map<Broker, Integer> brokerSalesCountList = new HashMap<Broker, Integer>();
private static ValueComparator<Broker> bvc =  new ValueComparator<Broker>(brokerSalesCountList);

在此处定义类：

public class ValueComparator<T> implements Comparator<T> {  
    Map<T, Integer> base;
    public ValueComparator(Map<T, Integer> base) {
        this.base = base;
    }
    @Override
    public int compare(T a, T b) {
        if (base.get(a) >= base.get(b)) {
            return -1;
        } else {
            return 1;
        } // returning 0 would merge keys
    }
}