equals

问题 I was reading the source code of EqualityComparer<T>.Default and found that it's not so clever. Here is an example: enum MyEnum : int { A, B } EqualityComparer<MyEnum>.Default.Equals(MyEnum.A, MyEnum.B) //is as fast as EqualityComparer<int>.Default.Equals(0, 1) enum AnotherEnum : long { A = 1L, B = 2L } //is 8x slower than EqualityComparer<long>.Default.Equals(1L, 2L) The reason is obvious from the source code of the private method in EqualityComparer. private static EqualityComparer<T>

问题 I'm here to ask a specific topic - I really found few info about this on the web. I'm implementing a F# version of Minimax algorithm. The problem I'm having now is that I want to compare Leaf of my tree (data structure below). Searching the erros the VS gave to me I arrived to something like this: The tree type I used to have: type TreeOfPosition = | LeafP of Position | BranchP of Position * TreeOfPosition list and the temptative for implementing the IComparable type staticValue = int [

问题 How can I compare if two json structures are the same in scala? For example, if I have: { resultCount: 1, results: [ { artistId: 331764459, collectionId: 780609005 } ] } and { results: [ { collectionId: 780609005, artistId: 331764459 } ], resultCount: 1 } They should be considered equal 回答1: You should be able to simply do json1 == json2 , if the json libraries are written correctly. Is that not working for you? This is with spray-json, although I would expect the same from every json library

问题 I have the classes below: public class Sample implements java.io.Serializable{ //POJO with two fields and getters/setters private String name; private Integer id; //This POJO does not override equals() and hashCode() } public class B{ private Sample sample; //here i need override hashcode and equals() based on **sample** property. } When i tried overriding equals() and hashCode() in the B class I got the error below in Eclipse. The field type com.mypackage.Sample does not implement hashCode()

问题 I want to see if a character in my string equals a certain other char value but I do not know what the char in the string is so I have used this: if ( fieldNames.charAt(4) == "f" ) But I get the error: "Operator '==' cannot be applied to 'char', 'jav.lang.String'" But "g" == "h" seems to work and I know you can use '==' with char types. Is there another way to do this correctly? Thanks! 回答1: if ( fieldNames.charAt(4) == 'f' ) because "f" is a String and fieldNames.charAt(4) is a char . you

问题 I have a Dictionary which I am comparing to another Dictionary (variables typed as IDictionary). Doing d1.Equals(d2) yields false. Writing my own code below yields true. Both are System.Collections.Generic.Dictionary . Am I missing something or does Dictionary not have an Equals implementation that compares keys/values? private static bool DictEquals<K, V>(IDictionary<K, V> d1, IDictionary<K, V> d2) { if (d1.Count != d2.Count) return false; foreach (KeyValuePair<K, V> pair in d1) { if (!d2

问题 Implementing equals() and hashCode() for simple data POJOs is cluttering my code and maintaining is tedious. What are the libraries handling this automatically? I prefer bytecode instrumentation over AOP approach due to performance reasons. Update: Topic of necessity of implementing equals() and hashCode() has been discussed, here's my point: Isn't it better to have it done right upfront with minimal effort rather than digging in the code, adding hC/eq when it comes to it? 回答1: Project Lombok

问题 I have an address object that I want to create an equals method for. I could have made this quite simple by doing something like the following (shortened a bit): public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; Address other = (Address) obj; return this.getStreet().equals(other.getStreet()) && this.getStreetNumber().equals(other.getStreetNumber()) && this.getStreetLetter().equals(other

问题 This question already has answers here : Closed 6 years ago . Possible Duplicate: Java: Checking equality of arrays (order doesnt matter) I have two arrays : String[] a1 = {"a", "b", "c"}; String[] a2 = {"c", "b", "a"}; I need to check if both contains same elements (and of same length) irrespective of order of elements. I tried Arrays.equals(a1, a2) but it considers order of element. org.apache.commons.lang.ArrayUtils does not provide this thing. I know I can achieve the same by creating my

问题 I always wondered why there's an equals keyword in linq joins rather than using the == operator. Property deadline = (from p in properties join w in widgets on p.WidgetID equals w.ID select p).First(); Instead of Property deadline = (from p in properties join w in widgets on p.WidgetID == w.ID select p).First(); [EDIT] Rephrased the question and revised the examples. 回答1: There's a nice explanation by Matt Warren at The Moth: "The reason C# has the word ‘equals’ instead of the ‘==’ operator