hashset

问题 I am coding in blueJ and what I am trying to do is this: 1.a) Create a getWordSet() method in WordGroup which: takes another WordGroup object as a parameter creates a HashSet<String> uses two for loops to put all the words from this and the parameter WordGroup into the HashSet returns the HashSet<String> 1.b) In the main method: use the getWordSet() method using the two WordGroup s iterate or loop over the HashSet returned and print the words from it 2.a) Create a method in the WordGroup

问题 This question already has answers here : How to convert int[] into List<Integer> in Java? (18 answers) Closed 2 years ago . I have code that looks like this: int[] ho = new int[10]; ho[0]= 1; ho[2]= 1; ho[4]= 5; HashSet<Integer> hs = new HashSet(Arrays.asList(ho)); Integer[] a = hs.toArray(new Integer[hs.size()]); This code makes perfect sense to me, but it throws an ArrayStoreException when I run it. Why is that? The HashSet is a set of Integer s, and so is the output array. 回答1:

问题 1. I understand the different hash map mechanisms and the ways in which key collisions are handled (either open addressing -linear/quadratic probing, chaining, extendable hashing, etc. Which one does HashSet/HashMap make use of? 2. I realise that a good HashMap relies on a good hash function. How does Java's HashSet/HashMap hash the objects? I know that there is a hash function but so far for strings I have not needed to implement this. What if I now want to Hash a Java Object that I create -

问题 I'm trying to see if HashSet would be the solution for my next project so i'm doing some very easy test to check functionalities. I have a simple class Klant : public class Klant { private int klantNummer; public Klant(int nummer) { this.klantNummer = nummer; } public int getKlantNummer() { return this.klantNummer; } } and a class with through composition uses a HashSet public class MySet<Klant> { private Collection<Klant> mySet = null; public MySet() { mySet=new HashSet<Klant>(); } public

问题 I'm having trouble finding the intersection of an Array of Hashed Sets that contain a data Class (where I want to intersect by identifier): class Protein(val id: String, val score: Double, val molw: Double, val spc: Int) I've pulled in some data from a .csv file into this type of structure: ArrayList<HashSet<Protein>> So I have six array lists [1 for each csv], each containing one hashed set that contains thousands of Protein structures. Here's what I've tried so far to get an intersection

问题 If you look at java's hashCode method inside hashMap, you will find: public int hashCode() { int h = 0; Iterator<Entry<K,V>> i = entrySet().iterator(); while (i.hasNext()) h += i.next().hashCode(); return h; } So when you insert things into hashMap, hashMap's hashCode will change. Thus, if we insert an empty hashMap into hashSet, then insert something to this hashMap, then call hashSet.contains(hashMap) , it will return false . Why does Java allow such behavior? This will easily cause

问题 If you look at java's hashCode method inside hashMap, you will find: public int hashCode() { int h = 0; Iterator<Entry<K,V>> i = entrySet().iterator(); while (i.hasNext()) h += i.next().hashCode(); return h; } So when you insert things into hashMap, hashMap's hashCode will change. Thus, if we insert an empty hashMap into hashSet, then insert something to this hashMap, then call hashSet.contains(hashMap) , it will return false . Why does Java allow such behavior? This will easily cause

问题 As I have an ArrayList of int arrays which contains duplicates, I'd like to use HashSet. Unfortunately, I can't manage to use HashSet as I wish: System.out.print("\nTESTs\n"); ArrayList<int[]> list = new ArrayList<int[]>(); list.add(new int[]{1,2,3}); list.add(new int[]{5,1,1}); list.add(new int[]{1,2,3});//duplicate list.add(new int[]{5,1,3}); Set<int[]> set = new HashSet<int[]>(list); System.out.println("Size of the set = "+set.size()); ArrayList<int[]> arrayList = new ArrayList<int[]>(set)

问题 In addition to this quite old post, I need something that will use primitives and give a speedup for an application that contains lots of HashSet s of Integers : Set<Integer> set = new HashSet<Integer>(); So people mention libraries like Guava, Javalution, Trove, but there is no perfect comparison of those in terms of benchmarks and performance results, or at least good answer coming from good experience. From what I see many recommend Trove's TIntHashSet , but others say it is not that good;

问题 The data First of all, let's generate some input so we have concrete data to talk about: python -c 'for f in xrange(4000000): print f' > input.txt this will generate a file input.txt containing the numbers from 0 to 3999999, each on its own line. That means we should have a file with 4,000,000 lines, adding up to 30,888,890 bytes, roughly 29 MiB. Everything as a list Right, let's load everything into memory as a [Text] : import Data.Conduit import Data.Text (Text) import Control.Monad.Trans