hashcode

How can I ensure closed dialogs are unregistered from INPC events?

由 ε祈祈猫儿з 提交于 2019-12-24 11:56:55
问题 I have an MVVM-Light based WPF application, with a dialog service (called WindowManager ) that opens up dialog windows bound to pre-initiated dialog view-models, like this: private enum ViewModelKind { PlanningGridVM, InputDialogVM, TreeViewDialogVM, SaveFileDialogVM, MessageBoxVM } /// <summary> /// Shows the Window linked to this ViewModel as a dialog window. /// </summary> /// <typeparam name="TViewModel">The type of the view model.</typeparam> /// <returns>Tri-state boolean dialog

How to write a proper hashcode method for double values with limited precision? [duplicate]

由 旧街凉风 提交于 2019-12-24 07:25:12
问题 This question already has an answer here : Should Equality Comparison of Float / Double Instance Variables in an Equals Method be Exact? (1 answer) Closed 5 months ago . An object of class Foo is considered equal if the double members are within a given range of the other object. Such an error can easily be introduced due to floating point arithmetic. The method isDoubleEquals and doubleArrayEquals will take care of the equals part but the contract states that the hashcode has to be identical

How to write a proper hashcode method for double values with limited precision? [duplicate]

由 泄露秘密 提交于 2019-12-24 07:25:04
问题 This question already has an answer here : Should Equality Comparison of Float / Double Instance Variables in an Equals Method be Exact? (1 answer) Closed 5 months ago . An object of class Foo is considered equal if the double members are within a given range of the other object. Such an error can easily be introduced due to floating point arithmetic. The method isDoubleEquals and doubleArrayEquals will take care of the equals part but the contract states that the hashcode has to be identical

Does Asp support Hash (bcrypt) Passwords like in PHP

由 点点圈 提交于 2019-12-24 06:44:55
问题 Is there a way to use Hash (bcrypt) Passwords in ASP like in PHP... the following would be the code for PHP but what is the alternative for ASP .. is it the same and just change things around? does ASP support Hash(bcrypt) or is there other way to do ? please engliten me with this situation... PHP would be $link = mysql_connect('localhost', 'wpscanner', 'aUvmxcxvTUPtW8Kw') or die('Not connected : ' . mysql_error()); mysql_select_db('wpscanner', $link) or die ('Not selected : ' . mysql_error()

8张图理解Java

由 雨燕双飞 提交于 2019-12-24 04:09:05
1、 字符串不变性 下面这张图展示了这段代码做了什么 1 2 String s = "abcd" ; s = s.concat( "ef" ); 2、 equals()方法、hashCode()方法的区别 HashCode被设计用来提高性能。equals()方法与hashCode()方法的区别在于： 如果两个对象相等(equal)，那么他们一定有相同的哈希值。 如果两个对象的哈希值相同，但他们未必相等(equal)。 3、 Java异常类的层次结构 图中红色部分为受检查异常。它们必须被捕获，或者在函数中声明为抛出该异常。 4、 集合类的层次结构 注意Collections和Collection的区别。（Collections包含有各种有关集合操作的静态多态方法） 5、 Java同步 Java同步机制可通过类比建筑物来阐明。 6、 别名 别名意味着有多个变量指向同一可被更新的内存块，这些别名分别是不同的对象类型。 7、 堆和栈 图解表明了方法和对象在运行时内存中的位置。 8、 Java虚拟机运行时数据区域 图解展示了整个虚拟机运行时数据区域的情况。 摘自：http://www.importnew.com/11725.html 来源： https://www.cnblogs.com/h07061108/p/Java_picture.html

dart, is xoring two hashcodes always going to return a new unique hashcode?

由 主宰稳场 提交于 2019-12-23 15:02:26
问题 I am writing a class that needs to have a unique hashcode based on two of its fields and I wanted to know whether XORing the 2 fields hashcodes is enough to generate a unique and consistent hashcode for my object? class _TypeMatch{ final Type _potentialSubtype; final Type _supertype; int _cachedHashCode; _TypeMatch(this._potentialSubtype, this._supertype){ _cachedHashCode = _potentialSubtype.hashCode ^ _supertype.hashCode; } int get hashCode => _cachedHashCode; bool operator ==(other){ return

when add key-value pair to a hashMap, why Java makes hashMap's hashCode change?

由 好久不见. 提交于 2019-12-23 14:51:34
问题 If you look at java's hashCode method inside hashMap, you will find: public int hashCode() { int h = 0; Iterator<Entry<K,V>> i = entrySet().iterator(); while (i.hasNext()) h += i.next().hashCode(); return h; } So when you insert things into hashMap, hashMap's hashCode will change. Thus, if we insert an empty hashMap into hashSet, then insert something to this hashMap, then call hashSet.contains(hashMap) , it will return false . Why does Java allow such behavior? This will easily cause

when add key-value pair to a hashMap, why Java makes hashMap's hashCode change?

由 ♀尐吖头ヾ 提交于 2019-12-23 14:51:14
问题 If you look at java's hashCode method inside hashMap, you will find: public int hashCode() { int h = 0; Iterator<Entry<K,V>> i = entrySet().iterator(); while (i.hasNext()) h += i.next().hashCode(); return h; } So when you insert things into hashMap, hashMap's hashCode will change. Thus, if we insert an empty hashMap into hashSet, then insert something to this hashMap, then call hashSet.contains(hashMap) , it will return false . Why does Java allow such behavior? This will easily cause

C#: Same Object have to Same HashCode?

由 跟風遠走 提交于 2019-12-23 14:46:27
问题 Let's assume I have two objects called K and M if(K.Equals(M)) { } If that's true, K and M always has the same HashCode ? Or It depends on the programming language ? 回答1: The contract for GetHashCode() requires it, but since anyone can make their own implementation it is never guaranteed. Many classes (especially hashtables) require it in order to behave correctly. If you are implementing a class, you should always make sure that two equal objects have the same hashcode. If you are

hashcode方法？是什么？

由 纵饮孤独 提交于 2019-12-23 13:52:44
hashcode方法？是什么？ 引用资源： https://www.jianshu.com/p/417a192125f6 概念： Java的Object类中有一个hashCode()方法，并且是本地方法，返回一个int类型数值 对于包含容器类型的程序设计语言来说，基本上都会涉及到hashCode。在Java中也一样，hashCode方法的主要作用是为了配合基于散列的集合一起正常运行，这样的散列集合包括HashSet、HashMap以及HashTable。 分析： 举个列子：当向集合中插入对象时，如何判别在集合中是否已经存在该对象？（集合中不允许重复的元素存在） 大多数人会想到equals方法来逐个进行比较，这个方法确实可行。但是如果集合中已经存在一万条数据或者更多的数据，效率必然是一个问题。所以，hashCode作用就体现出来了，当集合要添加新的对象时，先调用这个对象的hashCode方法，得到相应的hashCode值，实际上HashMap的具体实现中会用一个table保存已经存进去的对象的hashCode值，如果table中没有这个hashCode值，就可以直接存进去，不用再进行任何比较了；如果存在该hashCode值，就调用它的equals方法与新元素进行比较，相同的话就不存了，不相同就散列其他的地址，所以这里存在一个冲突解决的问题
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