LinkedHashSet：hashCode（）和equals（）匹配，但contains（）不匹配(LinkedHashSet: hashCode() and equals() match, but contains() doesn't)

 以下是如何可能的： 
 
void contains(LinkedHashSet data, Object arg) {
    System.out.println(data.getClass()); // java.util.LinkedHashSet
    System.out.println(arg.hashCode() == data.iterator().next().hashCode()); // true
    System.out.println(arg.equals(data.iterator().next())); // true
    System.out.println(new ArrayList(data).contains(arg)); // true
    System.out.println(new HashSet(data).contains(arg)); // true
    System.out.println(new LinkedHashSet(data).contains(arg)); // true (!)
    System.out.println(data.contains(arg)); // false
}
 
 难道我做错了什么？ 
 
 显然，它并不总是发生（如果你创建一组琐碎的对象，你将无法重现它）。 但它总是发生在我的情况下更复杂的arg类。 
 
 编辑 ：我没有在这里定义arg主要原因是它是相当大的类，Eclipse生成的hashCode跨越20行并且equals两倍。 而且我不认为它是相关的 - 只要它们对于这两个对象是相同的。 

How is the following possible:
 
void contains(LinkedHashSet data, Object arg) {
    System.out.println(data.getClass()); // java.util.LinkedHashSet
    System.out.println(arg.hashCode() == data.iterator().next().hashCode()); // true
    System.out.println(arg.equals(data.iterator().next())); // true
    System.out.println(new ArrayList(data).contains(arg)); // true
    System.out.println(new HashSet(data).contains(arg)); // true
    System.out.println(new LinkedHashSet(data).contains(arg)); // true (!)
    System.out.println(data.contains(arg)); // false
}
 
Am I doing something wrong?
 
Obviously, it doesn't always happen (if you create a trivial set of Objects, you won't reproduce it). But it does always happen in my case with more complicated class of arg.
 
EDIT: The main reason why I don't define arg here is that's it's fairly big class, with Eclipse-generated hashCode that spans 20 lines and equals twice as long. And I don't think it's relevant - as long as they're equal for the two objects.

原文：https://stackoverflow.com/questions/8007723