使用比较器帮助比较浮点型成员变量 [英] Help comparing float member variables using Comparators

问题描述

我可以很好地比较字符串，但是想知道如何对浮点数进行排名?

I am able to compare Strings fine, but would like to know how I can rank floating point numbers?

getChange()返回一个字符串.我希望能够对降序进行排序.我该怎么办?

getChange() returns a String. I want to be able to sort descending. How can I do this?

更新:

package org.stocktwits.helper;

import java.util.Comparator;

import org.stocktwits.model.Quote;

public class ChangeComparator implements Comparator<Quote>
{
    public int compare(Quote o1, Quote o2) {
        float change1 = Float.valueOf(o1.getChange());
        float change2 = Float.valueOf(o2.getChange());

        if (change1 < change2) return -1;
        if (change1 == change2) return 0; // Fails on NaN however, not sure what you want
        if (change2 > change2) return 1;
    }
}

我收到了编译时错误:

This method must return a result of type int    ChangeComparator.java   

推荐答案

阅读

Read the javadoc of Comparator#compare() method.

比较其两个参数的顺序. 当第一个参数小于，等于或大于第二个参数时，返回负整数，零或正整数.

因此，基本上:

float change1 = o1.getChange();
float change2 = o2.getChange();
if (change1 < change2) return -1;
if (change1 > change2) return 1;
return 0;

或者，如果您喜欢条件运算符:

Or if you like conditional operators:

return o1.getChange() < o2.getChange() ? -1 
     : o1.getChange() > o2.getChange() ? 1 
     : 0;

但是，您需要考虑 Float.NaN .我不确定您要如何订购它们.第一的?最后的?同样吗?

You however need to take account with Float.NaN. I am not sure how you'd like to have them ordered. First? Last? Equally?

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