Comparison method violates its general contract! Java 7 only

see this: From Area: API: Utilities Synopsis: Updated sort behavior for Arrays and Collections may throw an IllegalArgumentException 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 … Read more