equals

问题 I was trying this code writing exercise and I am so lost! The exercise is: Complete the method which takes two Strings and one boolean as input. If the boolean is true, this method compares the first two Strings, ignoring case considerations (uppercase/lowercase). Two Strings are considered equal ignoring case if they are of the same length, and corresponding characters in the two Strings are equal ignoring case. If the boolean is false, this method should compare two Strings and return true

问题 I know the contract says "if two objects are equal then they should return the same hash code". That is so that those objects can be place in the same hash bucket and to improve hash code related collection functions know. Then again why it says "if two objects have same hash code those should not always be equals". I mean if it is true in the contract we should say "if two objects are equals they may return same hash code but which is not mandatory" 回答1: I mean if it is true in the contract

问题 I know there are a lot of ways to compare VALUE and REFERENCES in C#, but I'm still a bit confused about what type performs what when you try to compare either VALUE or REFERENCE. String examples: string str = "hello"; string str2 = "hello"; if (str == str2) { Console.WriteLine("Something"); } // Is this a comparison of value? if (str.Equals(str2)) { Console.WriteLine("Something"); } // Is this a comparison of value? string.ReferenceEquals(str, str2); // Comparison of reference (True) Console

问题 This question already has answers here : Difference between Equals/equals and == operator? (11 answers) Closed 5 years ago . Suppose if I want to put a key and its value in a Map. I believe it is what Java does: Get the Hashcode of the key and check whether there is a key in the map with the same hashcode. If there is no key with the same Hashcode then the key can be put into Map. If there is a key with the same Hashcode then use equals to determine whether the key can be put into Map or not.

问题 I have the following situation: I need to sort trees based by height, so I made the Tree's comparable using the height attribute. However, I was also told to overwrite the equals and hashCode methods to avoid unpredictable behaviour. Still, sometimes I may want to compare the references of the roots or something along those lines using ==. Is that still possible or does the == comparison call the equals method? 回答1: equals() is meant to compare an object with rules set by the programmer. In

问题 I have two classes that represent two different database entities. Their relationship is 1:m in db and it is represented in class structures something like this: public class Company { private List<Employee> employees; public List<Employee> getEmployees() { return employees; } public void setEmployees(List<Employee> employees) { this.employees = employees; } } public class Employee { private Company company; public Company getCompany() { return company; } public void setCompany(Company

问题 I am developing an Android application which makes use of the ScanResult object. This object is in the form of: [SSID: __mynetwork__, BSSID: 00:0e:2e:ae:4e:85, capabilities: [WPA-PSK-TKIP][ESS], level: -69, frequency: 2457, timestamp: 117455824743] How would I override only the equals() method without creating a customer class which extends it in order to compare only the SSID , BSSID , capabilties , level and frequency attributes only? In other words, in the equals method I want to eliminate

问题 I am creating pie charts with JSON and Flot. The JS function to create the pie chart receives a JSON array from Django in this format: [1, 3, 2, 5, 4] If there is no data, the JSON array is: [0, 0, 0, 0, 0] I'm trying to adjust the function so that if there is no data, then the pie will not be plotted and some text will appear instead (e.g. "Nothing to show yet"). So far I have tried: function loadWeekChart(theData) { var blankData = [0, 0, 0, 0, 0]; if ($.data(theData) == $.data(blankData)){

问题 from p.46 "Effective Java" Joshua Bloch. Item 9: ALways override hashCode when you override equals Some class PhoneNumber overrides equals() and doesn't override hashCode() "two instances are involved: one is used for insertion into the HashMap, and a second, equal, instance is used for (attempted) retrieval." ... "... Even if the two instances happen to hash to the same bucket, the get method will almost certainly return null , as HashMap has an optimization that caches the hash code

问题 Is there a standard technique to "extend" a class with private constructors, as with most Singleton classes? Specifcally, I'm trying to extend the java.lang.management.ThreadInfo class because I'm adding a LOT of them to a HashSet to control uniqueness. However, the way I determine if two threads are equal is different and not identical to the default implementation of the equals() method. Extending the class is obviously not an option in this case. Would it be reasonable to make something