首先，你要比较的的距离的轨道和头部位置之间，所以你必须使用绝对值在你的条件。

First, you want to compare the distance between the track and the head position, so you have to use the absolute value in your conditions.

if (Math.abs(nextHeadPosition - r1.getTrackNumber())  < Math.abs(nextHeadPosition -  r2.getTrackNumber()))

但你的比方法修改的对象，这是不是一个好主意，因为你不知道如何 Col​​lections.sort（）（我想这是你想要使用的）将使用它。你必须编写自己的排序算法，我认为。

But your compare method modifies the object, which is not a good idea since you don't know how Collections.sort() (I guess that's what you're trying to use) will use it. You have to write your own sorting algorithm I think.