java - 使用比较器对列表进行排序后数字精度会丢失

Question

我有一个方法，可以根据“距离”属性比较填充有 DMatch 对象的任何给定列表。我现在遇到的问题是，我从排序列表中得到的距离类似于:

Debug: MainClass -> descriptorMatcher: Min_Dist: 0.070726834
Debug: MainClass -> descriptorMatcher: Max_Dist: 0.5799786

虽然它应该是这样的:

Info: MainClass -> descriptorMatcher: Max_Dist: 0.5799785852432251
Info: MainClass -> descriptorMatcher: Min_Dist: 0.07072683423757553

为什么我会失去数字精度以及如何避免它。

代码:

public static List<DMatch> getTopGoodMatches(List<DMatch> list, int startIndx, int range) {
    if (list != null) {
        if (!list.isEmpty()) {

            if (range != 0) {
                if ( (startIndx + range) <= list.size() ){
                    Log.V(TAG, "getTopGoodMatches", range + " match line(s) will be drawn");
                    Collections.sort(list, ascOrder);
                    return list.subList(startIndx, (startIndx + range));
                } else {
                    Log.E(TAG, "getTopGoodMatches", "(startIndx + range) must be <= the total list size");
                    return null;
                }
            } else {
                Log.E(TAG, "main", "range can not be zero");
                return null;
            }

        } else {
            Log.E(TAG, "getTopGoodMatches", "the list you passed to this method is empty, empty list can not be sorted.");
            return null;
        }
    } else {
        Log.E(TAG, "getTopGoodMatches", "the list you passed to this method is null, null object can not be sorted.");
        return null;
    }
}

private static Comparator<DMatch> ascOrder = new Comparator<DMatch>() {

    public int compare(DMatch arg0, DMatch arg1) {
        // TODO Auto-generated method stub
        return Double.compare(arg0.distance, arg1.distance);
    }
};

Answer 1

如果您需要任意精度的十进制值，则不能使用 float 或 double。请改用 BigDecimal。或者将其转换为非十进制值(int、long)并注意逻辑中的小数位数。

参见http://docs.oracle.com/javase/7/docs/api/java/math/BigDecimal.html