equals

I made the mistake of using == for comparing IP addresses instead of using the equals() method of the IPAddress class in C#, which will result in the comparison of references instead of values. Since the solution I am currently working on is very large for a one-man project (> 100.000 lines of source code), I am very sure that I still have some of these wrong statements in my code. Is there any possibility to tell Visual Studio to find all occurrences of == operations on a specific class for me, so that I can find and clean up the bugged comparisons? with best regards, emi It's a bit of a hack

Given this: String s1= new String("abc"); String s2= new String("abc"); String s3 ="abc"; System.out.println(s1==s3); System.out.println(s1==s2); System.out.println(s1.equals(s2)); System.out.println(s1.equals(s3)); System.out.println(s1.hashCode()); System.out.println(s2.hashCode()); System.out.println(s3.hashCode()); Output is: false false true true 96354 96354 96354 Here == is giving false for each object but the hashcode for each String object is same. Why is it so? == does compare real equality of objects (I mean - both references point to the same object), not their content, whereas

Everytime I write some data class, I usually spend so much time writing the IEquatable implementation. The last class I wrote was something like: public class Polygon { public Point[] Vertices { get; set; } } Implementing IEquatable was exaustive. Surely C#3.0/LINQ helps a lot, but the vertices can be shifted and/or in the reverse order, and that adds a lot of complexity to the Equals method. After many unit tests, and corresponding implementation, I gave up, and changed my application to accept only triangles, which IEquatable implementation required only 11 unit tests to be fully covered.

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.ContainsKey(pair.Key)) return false; if (!Equals(d2[pair.Key], pair.Value)) return false; } return true;

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.getStreetLetter()) && this.getTown().equals(other.getTown()); } Problem is, some of these might be null. I will in

I can't find any documentation on "not equal" sign in Visual Prolog. Please provide the right solution of this problem: class predicates sister : (string Person, string Sister) nondeterm(o,o). clauses sister(Person, Sister) :- Person [not-equal-sign] Sister, parent(Person, Parent), parent(Sister, Parent), woman(Sister). I don't know what do you mean by "not equal" (does not unify?), but you could try these: X \= Y not(X = Y) \+ (X = Y) Documentation for the second variant pointed out by Kaarel can be found in this Visual Prolog reference page. However the problem with your code goes a little

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? Project Lombok provides the annotation @EqualsAndHashCode which will generate equals() and hashCode() for your Java