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POComparison method violates its general contract! Java 7 only
 

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  1. POComparison method violates its general contract! Java 7 only
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    <p>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.</p> <p>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.</p> <p>This method worked great as long as it was running with java &lt; 7. But since Java 7 I keep getting this one:</p> <pre><code>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) </code></pre> <p>Here is the source, where some potentially dangerous parts have allready been out-commented, but it still does not work:</p> <pre><code>public class crew implements Serializable, Comparable&lt;crew&gt; { 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 &gt; hisRank) { return 1; } if (myRank &lt; hisRank) { return -1; } if (myRank == hisRank) { // if (is_trainer &amp;&amp; !o.is_trainer) { // i = 1; // } // if (!is_trainer &amp;&amp; o.is_trainer) { // i = -1; // } // if (is_trainer &amp;&amp; o.is_trainer) { // i = 0; // } // if (!is_trainer &amp;&amp; !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 &gt; hisRank) { return false; } if (myRank &lt; hisRank) { return false; } if (myRank == hisRank) { // if (is_trainer &amp;&amp; !o.is_trainer) { // i = 1; // } // if (!is_trainer &amp;&amp; o.is_trainer) { // i = -1; // } // if (is_trainer &amp;&amp; o.is_trainer) { // i = 0; // } // if (!is_trainer &amp;&amp; !o.is_trainer) { // i = 0; // } return true; } return false; } </code></pre> <p>}</p> <p>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</p>
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    1. USMarek Sebera
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      1. POComparison method violates its general contract! Java 7 only
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    1. COCan you show the code where you're doing the sort ?
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      1. POComparison method violates its general contract! Java 7 only
      1. USWilQu
    2. COAnd what's the difference between assigned_rank and getAssigned_rank()?
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      1. POComparison method violates its general contract! Java 7 only
      1. USRaymond Chen
    3. COsimilar question asked [here](http://stackoverflow.com/questions/6626437/why-does-my-compare-method-throw-exception-comparison-method-violates-its-gen)
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      1. POComparison method violates its general contract! Java 7 only
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