java-collections.sort异常Comparison method violates its general contract!

Posted 2020-08-01 y酒味i

转载:http://www.tuicool.com/articles/MZreyuv

异常信息

java.lang.IllegalArgumentException: Comparison method violates its general contract!
 at java.util.TimSort.mergeHi(TimSort.java:868)
  at java.util.TimSort.mergeAt(TimSort.java:485)
  at java.util.TimSort.mergeCollapse(TimSort.java:408)
at java.util.TimSort.sort(TimSort.java:214)
  at java.util.TimSort.sort(TimSort.java:173)
  at java.util.Arrays.sort(Arrays.java:659)
  at java.util.Collections.sort(Collections.java:217)
...

 

原因

JDK7中的Collections.Sort方法实现中，如果两个值是相等的，那么compare方法需要返回0，否则 可能 会在排序时抛错，而JDK6是没有这个限制的。

if (len2 == 0) {
    throw new IllegalArgumentException("Comparison method violates its general contract!");
}