比较方法违反其一般合同！仅Java 7 [英] Comparison method violates its general contract! Java 7 only

问题描述

我知道这已经有一段时间了，并检查了我可以获得的所有先前答案，但是仍然无法解决问题.

I know this has been an issue for a while now, and checked all previously answers I could get, but still this one doesn't work.

对象船员"代表具有等级和其他项目的机组人员.应该通过比较int值'assigned_rank'进行比较，如果在两个实例中该值都相等，则布尔值'is_trainer'应该有所不同.

The object 'crew' represents crewmembers with ranks and other items. The comparison should be made by comparing 'assigned_rank', an int value, and if this value is equal in both instances, then 'is_trainer', a boolean, should make the difference.

只要与Java<一起运行，此方法就可以很好地工作. 7.但是自Java 7以来，我一直得到这个:

This method worked great as long as it was running with java < 7. But since Java 7 I keep getting this one:

java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.util.ComparableTimSort.mergeLo(ComparableTimSort.java:714)
at java.util.ComparableTimSort.mergeAt(ComparableTimSort.java:451)
at java.util.ComparableTimSort.mergeCollapse(ComparableTimSort.java:376)
at java.util.ComparableTimSort.sort(ComparableTimSort.java:182)
at java.util.ComparableTimSort.sort(ComparableTimSort.java:146)
at java.util.Arrays.sort(Arrays.java:472)
at java.util.Collections.sort(Collections.java:155)
at dormas_flightlog.Query.getCrew(Query.java:714)

这里是消息来源，其中一些潜在危险部分已经被注释掉，但是仍然无法正常工作:

Here is the source, where some potentially dangerous parts have allready been out-commented, but it still does not work:

public class crew implements Serializable, Comparable<crew> {

private static final long serialVersionUID = 36L;
private int flightID = 0;
private int assigned_rank = 25;
private boolean is_trainer = false;
...


@Override
public int compareTo(crew him) {

    int myRank = this.getAssigned_rank();
    int hisRank = him.assigned_rank;

    if (this == him) {
        return 0;
    }
    if (myRank > hisRank) {
        return 1;
    }
    if (myRank < hisRank) {
        return -1;
    }
    if (myRank == hisRank) {
//            if (is_trainer && !o.is_trainer) {
//                i = 1;
//            }
//            if (!is_trainer && o.is_trainer) {
//                i = -1;
//            }
//            if (is_trainer && o.is_trainer) {
//                i = 0;
//            }
//            if (!is_trainer && !o.is_trainer) {
//                i = 0;
//            }
        return 0;
    }

    return 0;
}

@Override
public int hashCode() {
    int hash = 7;
    hash = 31 * hash + this.assigned_rank;
    hash = 31 * hash + (this.is_trainer ? 1 : 0);
    return hash;
}

@Override
public boolean equals(Object o) {

    if (this == o) {
        return true;
    }


    int myRank = this.getAssigned_rank();
    int hisRank = 0;

    if (o instanceof crew) {
        crew him = (crew) o;
        hisRank = him.assigned_rank;
    } else {
        return false;
    }

    if (myRank > hisRank) {
        return false;
    }
    if (myRank < hisRank) {
        return false;
    }
    if (myRank == hisRank) {
//            if (is_trainer && !o.is_trainer) {
//                i = 1;
//            }
//            if (!is_trainer && o.is_trainer) {
//                i = -1;
//            }
//            if (is_trainer && o.is_trainer) {
//                i = 0;
//            }
//            if (!is_trainer && !o.is_trainer) {
//                i = 0;
//            }
        return true;
    }

    return false;
}

}

实现equals()只是解决此问题的一种尝试.给定的异常带有或不带有equals().我看不到compareTo方法如何违反其合同.非常感谢您的帮助....有一天此代码必须与Java 7兼容，我不知道如何... 谢谢

Implementing equals() was just a try to solve this problem. The given exception comes with or without equals(). I cannot see how the compareTo-method violates its contract. Any help is greatly appreciated....one day this code has to work with java 7 and I don't know how... Thanks

推荐答案

请参见:

来自 http://www.oracle.com/technetwork/java/javase/ibility-417013.html#source

区域:API:实用程序简介:更新了数组和数组的排序行为 集合可能会抛出IllegalArgumentException

Area: API: Utilities Synopsis: Updated sort behavior for Arrays and Collections may throw an IllegalArgumentException

描述:java.util.Arrays.sort和 (间接)由java.util.Collections.sort代替.新的 如果排序实现检测到，则可能抛出IllegalArgumentException 违反可比合同的可比公司.以前的 实施默默地忽略了这种情况.如果以前 行为是所希望的，您可以使用新系统 属性java.util.Arrays.useLegacyMergeSort，以还原先前的 mergesort行为.

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.

不兼容的性质:行为

RFE:6804124

RFE: 6804124

有关更多详细信息，请参见错误数据库参考此处.

For more detailed info, see the bug database reference here.

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