java错误Comparison method violates its general contract!

今天用到Collections.sort();方法时，提示错误如下：

网上查到一个解释：

Description: The sorting algorithm used by java.util.Arrays.sort and (indirectly) by java.util.Collections.sort has been replaced. The new sort implementation may throw an IllegalArgumentException if it detects a Comparable that violates the Comparable contract. The previous implementation silently ignored such a situation. If the previous behavior is desired, you can use the new system property, java.util.Arrays.useLegacyMergeSort, to restore previous mergesort behavior.

也就是说jdk 7的sort函数的实现变了，造成了这个问题，具体原因未知。

网上找了解决方法，如下

加入一句代码

<span style="font-size:14px;">System.setProperty("java.util.Arrays.useLegacyMergeSort", "true");</span>

转载出处： http://blog.csdn.net/fanzitao/article/details/8040201