hashset

Efficient way to clone a HashSet?

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If you really wanted the most efficient way to clone a HashSet<T>, you’d do the following (but possibly at the cost of maintainability) Use reflector or the debugger to figure out exactly what fields in HashSet<T> need to be copied. You may need to do this recursively for each field. Use Reflection.Emit or use expression … Read more

What’s better for creating distinct data structures: HashSet or Linq’s Distinct()?

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Anthony Pegram has said it the best. Use the right tool for the job. I say this because a Distinct or HashSet isn’t that big different when it comes to performance. Use a HashSet when the collection should always hold only distinct stuffs. It also tells the programmer that you cant add duplicates to it. … Read more

Java all determine elements are same in a list

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Using the Stream API (Java 8+) boolean allEqual = list.stream().distinct().limit(2).count() <= 1 or boolean allEqual = list.isEmpty() || list.stream().allMatch(list.get(0)::equals); Using a Set: boolean allEqual = new HashSet<String>(tempList).size() <= 1; Using a loop: boolean allEqual = true; for (String s : list) { if(!s.equals(list.get(0))) allEqual = false; } Issues with OP’s code Two issues with your … Read more

How can I convert a Java HashSet to a primitive int array?

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You can create an int[] from any Collection<Integer> (including a HashSet<Integer>) using Java 8 streams: int[] array = coll.stream().mapToInt(Number::intValue).toArray(); The library is still iterating over the collection (or other stream source) on your behalf, of course. In addition to being concise and having no external library dependencies, streams also let you go parallel if you … Read more

Hashtable, HashMap, HashSet , hash table concept in Java collection framework

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Java’s Set and Map interfaces specify two very different collection types. A Set is just what it sounds like: a collection of distinct (non-equal) objects, with no other structure. A Map is, conceptually, also just what it sounds like: a mapping from a set of objects (the distinct keys) to a collection of objects (the … Read more

HashSet allows duplicate item insertion – C#

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I’m guessing that you are creating a new Quotes with the same values. In this case they are not equal. If they should be considered equal, override the Equals and GetHashCode methods. public class Quotes{ public string symbol; public string extension public override bool Equals(object obj) { Quotes q = obj as Quotes; return q … Read more

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