JDK1.7 不兼容compare方法

java.lang.IllegalArgumentException: Comparison method violates its general contract!

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。

改一下系统设置，还是选择使用老版本的排序方法，在代码前面加上这么一句话：System.setProperty("java.util.Arrays.useLegacyMergeSort", "true");

// return a_actorDetails1.getId() - a_actorDetails2.getId() 改为一下
// double 直接return不支持。
if (a_actorDetails1.getId() - a_actorDetails2.getId() > 0) {
                comparisonResult = 1;
            }
            else if (a_actorDetails1.getId() - a_actorDetails2.getId() == 0) {
                comparisonResult = 0;
            }
            else {
                comparisonResult = -1;
            }
            break;