linkedhashset


Does hibernate preserve the order of a LinkedHashSet and if so, how?

余生长醉 提交于 2019-12-21 07:14:05
问题 Does hibernate preserve the order of a LinkedHashSet and if so, how? In case this depends on the type of database, I'd like to know this for PostgreSQL. Background: I know what a LinkedHashSet is for, and the reason I'm asking this is because I'm logging the names of some functions I execute to a 'logError' table that has a many-to-many relation to some 'functionName' table. I need these functions to remain in the same order as when I executed them, so first I find the corresponding

LinkedHashSet - insertion order and duplicates - keep newest “on top”

微笑、不失礼 提交于 2019-12-18 18:49:52
问题 I need a collection that keeps insertion order and has unique values. LinkedHashSet looks like the way to go, but there's one problem - when two items are equal, it removes the newest one (which makes sense), here's an example: set.add("one"); set.add("two"); set.add("three"); set.add("two"); The LinkedHashSet will print: one , two , three But what I need is: one , three , two What would be the best solution here? Is there any collection/collections method that can do this or should I

LinkedHashSet - insertion order and duplicates - keep newest “on top”

☆樱花仙子☆ 提交于 2019-12-18 18:49:09
问题 I need a collection that keeps insertion order and has unique values. LinkedHashSet looks like the way to go, but there's one problem - when two items are equal, it removes the newest one (which makes sense), here's an example: set.add("one"); set.add("two"); set.add("three"); set.add("two"); The LinkedHashSet will print: one , two , three But what I need is: one , three , two What would be the best solution here? Is there any collection/collections method that can do this or should I

What is the main difference between Hashset, Treeset and LinkedHashset, Hashmap and how does it work in Java?

我们两清 提交于 2019-12-18 07:08:27
问题 I just understand that LinkedHashSet does not allows duplicate elements when it is inserting. But, I dont understand how does Hashset works in Hava? I know a bit that Hashtable is used in Hashset so the hashtable used to store the elements and here also does not allow the duplicate elements. Then, Treeset is also similar to Hashset it also does not allows duplicate entries so unique elements will be seen and it follows ascending order. I have one more doubt regarding HashMap - Hashmap does

How iteration ordering in LinkHashMap/LinkedHashSet leads to a bit low performance than HashMap

笑着哭i 提交于 2019-12-11 10:37:46
问题 As LinkedHashMap/Set keeps the order of entry in the Collection so it leads to a little lower performance. I want to know why this happens. 回答1: LinkedHash[Map/Set] use doubly linked lists to keep track of the order of entries. So whenever an element is added, a new DLL node must be created. The allocation takes time, and several extra pointers need to be set. 回答2: The question is making the invalid assumption that LinkedHash[Map/Set]s always perform worse than their non-linked counterparts.

what's the difference between HashSet and LinkedHashSet

℡╲_俬逩灬. 提交于 2019-12-11 04:43:00
问题 I saw that LinkedHashSet extends HashSet and I know it preserves order. However, from checking the code in the JDK it seems that LinkedHashSet contains only constuctor and no implementation, so I guess all the logic happens in HashSet ? If that is correct, why is it designed like that? it seems very confusing. EDIT: there was an unfortunate mistake in the question. I wrote HashMap and LinkedHashMap instead of HashSet and LinkedHashSet . I fixed the question answer it if possible. Also, I was

Ordered insertion in linkedHashSet, any performant way ?

给你一囗甜甜゛ 提交于 2019-12-02 07:01:49
问题 So I have a LinkedHashSet , with values say a1, a2, , b, c1, c2 I want to replace, b with x , such that the order of x should be same as order of b. One obvious way would be private LinkedHashSet<String> orderedSubstitution(final Set<String> originalOrderedSet, final String oldItem, final String newItem) { final LinkedHashSet<String> newOrderedSet = new LinkedHashSet<String>(); // Things we do to maintain order in a linkedHashSet for (final String stringItem : originalOrderedSet) { if

Ordered insertion in linkedHashSet, any performant way ?

折月煮酒 提交于 2019-12-02 04:08:05
So I have a LinkedHashSet , with values say a1, a2, , b, c1, c2 I want to replace, b with x , such that the order of x should be same as order of b. One obvious way would be private LinkedHashSet<String> orderedSubstitution(final Set<String> originalOrderedSet, final String oldItem, final String newItem) { final LinkedHashSet<String> newOrderedSet = new LinkedHashSet<String>(); // Things we do to maintain order in a linkedHashSet for (final String stringItem : originalOrderedSet) { if (stringItem.equals(oldItem)) { newOrderedSet.add(newItem); } else { newOrderedSet.add(stringItem); } } return

LinkedHashSet .equals() vs LinkedList .equals() with same elements but different order

﹥>﹥吖頭↗ 提交于 2019-12-01 04:19:25
Consider the following SSCCE: public static void main(String[] args) { LinkedHashSet<String> set1 = new LinkedHashSet<>(); set1.add("Bob"); set1.add("Tom"); set1.add("Sam"); LinkedHashSet<String> set2 = new LinkedHashSet<>(); set2.add("Sam"); set2.add("Bob"); set2.add("Tom"); System.out.println(set1); System.out.println(set2); System.out.println(set1.equals(set2)); } This prints: [Bob, Tom, Sam] [Sam, Bob, Tom] true Yet if you change LinkedHashSet to LinkedList : public static void main(String[] args) { LinkedList<String> set1 = new LinkedList<>(); set1.add("Bob"); set1.add("Tom"); set1.add(

LinkedHashSet .equals() vs LinkedList .equals() with same elements but different order

拟墨画扇 提交于 2019-12-01 00:34:39
问题 Consider the following SSCCE: public static void main(String[] args) { LinkedHashSet<String> set1 = new LinkedHashSet<>(); set1.add("Bob"); set1.add("Tom"); set1.add("Sam"); LinkedHashSet<String> set2 = new LinkedHashSet<>(); set2.add("Sam"); set2.add("Bob"); set2.add("Tom"); System.out.println(set1); System.out.println(set2); System.out.println(set1.equals(set2)); } This prints: [Bob, Tom, Sam] [Sam, Bob, Tom] true Yet if you change LinkedHashSet to LinkedList : public static void main

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