hashset

问题 As an educational exercise, I'm looking at porting cvs-fast-export to Rust. Its basic mode of operation is to parse a number of CVS master files into a intermediate form, and then to analyse the intermediate form with the goal of transforming it into a git fast-export stream. One of the things that is done when parsing is to convert common parts of the intermediate form into a canonical representation. A motivating example is commit authors. A CVS repository may have hundreds of thousands of

问题 What the difference between HashSet.Union vs HashSet.Unionwith when i combine 2 hashsets. I am trying to combine like this: HashSet<EngineType> enginesSupportAll = _filePolicyEvaluation.EnginesSupportAll; enginesSupportAll = enginesSupportAll != null ? new HashSet<EngineType>(engines.Union(enginesSupportAll)) : enginesSupportAll; what is the best method for this example and why? 回答1: Well, it's not HashSet.Union but Enumerable.Union, so you are using a LINQ extension method that works with

问题 What the difference between HashSet.Union vs HashSet.Unionwith when i combine 2 hashsets. I am trying to combine like this: HashSet<EngineType> enginesSupportAll = _filePolicyEvaluation.EnginesSupportAll; enginesSupportAll = enginesSupportAll != null ? new HashSet<EngineType>(engines.Union(enginesSupportAll)) : enginesSupportAll; what is the best method for this example and why? 回答1: Well, it's not HashSet.Union but Enumerable.Union, so you are using a LINQ extension method that works with

问题 JavaDoc defines set as : A collection that contains no duplicate elements. More formally, sets contain no pair of elements e1 and e2 such that e1.equals(e2) To verify the same, i created a very simple program: import java.util.HashSet; public class CheckHashSet { public static void main(String[] args) { HashSet<Employee> set = new HashSet<Employee>(); set.add(new Employee(10)); set.add(new Employee(10)); System.out.println(set.size()); System.out.println(new Employee(10).equals(new Employee

问题 Please, suggest the shortest way to convert Dictionary<Key, Value> to Hashset<Value> Is there built-in ToHashset() LINQ extension for IEnumerables ? Thank you in advance! 回答1: var yourSet = new HashSet<TValue>(yourDictionary.Values); Or, if you prefer, you could knock up your own simple extension method to handle the type inferencing. Then you won't need to explicitly specify the T of the HashSet<T> : var yourSet = yourDictionary.Values.ToHashSet(); // ... public static class

问题 I am trying to determine to see if all elements in a list are same. such as: (10,10,10,10,10) --> true (10,10,20,30,30) --> false I know hashset might be helpful, but i don't know how to write in java. this is the one I've tried, but didn't work: public static boolean allElementsTheSame(List<String> templist) { boolean flag = true; String first = templist.get(0); for (int i = 1; i< templist.size() && flag; i++) { if(templist.get(i) != first) flag = false; } return true; } 回答1: Using the

问题 I am trying to determine to see if all elements in a list are same. such as: (10,10,10,10,10) --> true (10,10,20,30,30) --> false I know hashset might be helpful, but i don't know how to write in java. this is the one I've tried, but didn't work: public static boolean allElementsTheSame(List<String> templist) { boolean flag = true; String first = templist.get(0); for (int i = 1; i< templist.size() && flag; i++) { if(templist.get(i) != first) flag = false; } return true; } 回答1: Using the

问题 I am trying to determine to see if all elements in a list are same. such as: (10,10,10,10,10) --> true (10,10,20,30,30) --> false I know hashset might be helpful, but i don't know how to write in java. this is the one I've tried, but didn't work: public static boolean allElementsTheSame(List<String> templist) { boolean flag = true; String first = templist.get(0); for (int i = 1; i< templist.size() && flag; i++) { if(templist.get(i) != first) flag = false; } return true; } 回答1: Using the

问题 I've read this question: Changing the elements in a set changes the 'equals' semantics However, I don't know how to solve the problem that I can't change an item in the HashSet and remove it later. I have some example sourcecode: public static void main(String[] args) { TestClass testElement = new TestClass("1"); Set<TestClass> set = new HashSet<>(); set.add(testElement); printIt(testElement, set, "First Set"); testElement.setS1("asdf"); printIt(testElement, set, "Set after changing value");

问题 Newbie question about java HashSet Set<User> s = new HashSet<User>(); User u = new User(); u.setName("name1"); s.add(u); u.setName("name3"); System.out.println(s.contains(u)); Can someone explain why this code output false ? Moreover this code does not even call equals method of User. But according to the sources of HashSet and HashMap it have to call it. Method equals of User simply calls equals on user's name. Method hashCode return hashCode of user's name 回答1: If the hash code method is