hashcode

问题 I would like to use the @EqualsAndHashCode annotation on my domain classes, but it seems the equals and hashCode methods generated by that annotation don't take hasMany fields into account. I don't see any way to change this with the annotation, but I'm hoping that I'm missing something because it is very convenient (if it works). 回答1: Define the hasMany relationship as a Set in the parent domain class, which we normally do not do as it is redundant. You also have to make sure you are using

问题 I am looking for a specific hashcode that has the following properties. I dont know of any such hashcodes and I dont know if it is possible to do such a thing. Just wanted to put it out there and see what people say. I have two databases (loosely used term - dont think of SQL or anything of that sort), one master and one backup. There is a need to keep the two databases in sync and to detect when the databases are not in sync. Instead of verifying every data in there, it would be preferable

问题 We known that default implementation of hashCode() returns integer after converting the internal address converting the internal address of the object into an integer . So internal memory of every object is different, then why hashCode() does not generate unique hashcode. My question is why hashcode() [It returns integer which is address representation of an object] does not generate unique code , if we don't override hashcode() and equals? 回答1: Because it can't. Since there are only 2^32

问题 The hashCode of a java Hashtable element is always unique? If not, how can I guarantee that one search will give me the right element? 回答1: Not necessarily. Two distinct (and not-equal) objects can have the same hashcode. 回答2: First thing first. You should consider to use HashMap instead of Hashtable, as the latter is considered obsolete (it enforces implicit synchronization, which is not required most of the time. If you need a synchronized HashMap, it is easily doable) Now, regarding your

问题 I have a page with sticky menu bar in top. There are some internal links on this page. when I click on internal link, page scrolls and element having hashcode id moves to top. but heading hides in sticky menu. So on window load I have written js code, see below: if(window.location.hash) { var hash = window.location.hash.substring(1); //Puts hash in variable, and removes the # character console.log (hash); if(hash && $("#"+hash).length){ $("#"+hash).css('padding-top', '80px'); } $(window)

问题 so I'm not well versed in overriding hashCode and I seem to have some infinite recursion somehow going on with the hashCode method. Here is my scenario, I have a class DuplicateCache that is a cache object that checks for duplicate objects in our system. I have a static inner class Duplicate which represents the Duplicate objects. The DuplicateCache maintains a HashMap to keep track of all its entries. Each entry consists of a Duplicate object as the key and a Long object as the value. I am

问题 I am writing a simple program as follow: Given two numbers M and N, p is from [M,N] and q is from [1,p-1], find all irreducible fractions of p/q. My idea is brute force all possible value of p, q. And using HashSet to avoid duplicated fraction. However, somehow the contains function not working as expected. My code import java.util.HashSet; import java.util.Set; public class Fraction { private int p; private int q; Fraction(int p, int q) { this.p = p; this.q = q; } public static int getGCD

问题 Why does this code give a negative hashcode? import java.util.HashSet; import java.util.Set; public class Ab { /** * @param args */ public static void main(String[] args) { String s1="Operations on a dynamic set can be grouped into two categories queries, which simply return information about the set, and modifying operations, which change the set. Here is a list of typical operations. Any specific application will usually require only a few of these to be implemented Some dynamic sets

问题 A really simple question: I am doing a simple thing. I have few string like: string A = "usd"; And I want to get the hashcode in C#: int audusdReqId = Convert.ToInt32("usd".GetHashCode()); Now how could I convert the 32-bit integer audusdReqId back to the string "usd"? 回答1: You cannot. A hash code does not contain all of the necessary information to convert it back to a string. More importantly, you should be careful what you use GetHashCode for. This article explains what you should use it

问题 The following code is my attempt at a fairly generic javascript hash code implementation. I'm planning to use this code in conjunction with a hash table implementation (e.g. jshashtable) that utilizes hashCode() if its defined for keys. I have attempted to adhere closely to java's hash code implementations for numbers, strings, and arrays. Questions: Are there any issues with this implementation regarding correctness or performance? Are there any pre-existing implementations for hash codes