Comments (7)
@danielzhangy that behaviour is by design, I just have to write that in the documentation.
Not sure why java does it this way, but I used their ideology: https://docs.oracle.com/javase/7/docs/api/java/util/LinkedHashMap.html
... . Note that insertion order is not affected if a key is re-inserted into the map. (A key k is reinserted into a map m if m.put(k, v) is invoked when m.containsKey(k) would return true immediately prior to the invocation.). ...
I followed their documentation as not to be "smart" about it, but it can be implemented either way.
from gods.
@emirpasic I think the reason that java does it this way is that java wants the iterative sequence of LinkedHashMap to be close to the k-v entry input order, it is more ergonomic.
from gods.
@danielzhangy yes, I suppose it all depends at how we define "insertion".
Does placing the same element into set or map constitute insertion? According to Java, they don't treat it as a new insertion. I am really not sure about this one, might get philosophical :D
I will leave this question open in case somebody else has an opinion on this, for now I leave it with the Java's idea of what "insertion" really means.
from gods.
@emirpasic yes, it depends on the definition of "insertion".
Thanks to your reminder, I read the source code of Java 11. Java treats the same element placing in two different ways, it depends on the initial condition named accessOrder. If accessOrder is false, Java treats the same element placing as updating, otherwise, Java treats it as a special new insertion(updating the value of mapping key and moving the element to the tail of order list).
final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
boolean evict) {
Node<K,V>[] tab; Node<K,V> p; int n, i;
if ((tab = table) == null || (n = tab.length) == 0)
n = (tab = resize()).length;
if ((p = tab[i = (n - 1) & hash]) == null)
tab[i] = newNode(hash, key, value, null);
else {
Node<K,V> e; K k;
if (p.hash == hash &&
((k = p.key) == key || (key != null && key.equals(k))))
e = p;
else if (p instanceof TreeNode)
e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
else {
for (int binCount = 0; ; ++binCount) {
if ((e = p.next) == null) {
p.next = newNode(hash, key, value, null);
if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
treeifyBin(tab, hash);
break;
}
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k))))
break;
p = e;
}
}
if (e != null) { // existing mapping for key
V oldValue = e.value;
if (!onlyIfAbsent || oldValue == null)
e.value = value;
afterNodeAccess(e);
return oldValue;
}
}
++modCount;
if (++size > threshold)
resize();
afterNodeInsertion(evict);
return null;
}
void afterNodeAccess(Node<K,V> e) { // move node to last
LinkedHashMap.Entry<K,V> last;
if (accessOrder && (last = tail) != e) {
LinkedHashMap.Entry<K,V> p =
(LinkedHashMap.Entry<K,V>)e, b = p.before, a = p.after;
p.after = null;
if (b == null)
head = a;
else
b.after = a;
if (a != null)
a.before = b;
else
last = b;
if (last == null)
head = p;
else {
p.before = last;
last.after = p;
}
tail = p;
++modCount;
}
}
from gods.
@danielzhangy thanks for the research, it gave me an idea that it's best to have both. I think I'll add that option also to the LinkedHashSet and LinkedHashMap to configure this behavior or specialized functions that behave in one or the other way. Hwever, oI am still not sure what the default behavior should be, should the same element be evicted upon reinsertion and added to the end or should the default behavior follow Java's default behavior, i.e. no change in insertion order.
from gods.
@emirpasic I prefer to choose current implementation as default behavior, and make another way as optional, by considering the performance of operation. So what do you think?
from gods.
@danielzhangy i agree with you and i'll leave the current implementation as default, but will provide a way to modify this behavior.
from gods.
Related Issues (20)
- Add to Go official wiki? HOT 3
- generic upgrade request HOT 3
- RedBlackTree: Iterators become invalid after removing an element. HOT 2
- DS which can give element if present or next greater if not present, elements should be stored in sorted order HOT 2
- LinkedHashMap Sort? HOT 3
- Multiset support HOT 1
- deque support
- hashset should support NewWith Comparator
- Add method of Set lack info about the insert take place or not
- treeset:The names of each element are not equal, why is second_8 disappearing? HOT 1
- godslist.js refrence in chrome 120.0.6099.225 console
- Add elements of a slice [] T
- Red black tree: Unresolved reference 'NewWithIntComparator'
- Red black tree: package cmp is not in GOROOT (/usr/lib/golang/src/cmp)
- Interfaces support any types HOT 5
- Why cannot index priorityqueue.NewWith (value of type func(comparator utils.Comparator) *priorityqueue.Queue)? HOT 1
- A issue In BinaryHeap
- linkedhashmap json.Marshal error HOT 1
- treeset json.Unmarshal error HOT 1
- Update documention to use V2 version of generics
Recommend Projects
-
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
-
Vue.js
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
-
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
-
TensorFlow
An Open Source Machine Learning Framework for Everyone
-
Django
The Web framework for perfectionists with deadlines.
-
Laravel
A PHP framework for web artisans
-
D3
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
-
Recommend Topics
-
javascript
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
-
web
Some thing interesting about web. New door for the world.
-
server
A server is a program made to process requests and deliver data to clients.
-
Machine learning
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
-
Visualization
Some thing interesting about visualization, use data art
-
Game
Some thing interesting about game, make everyone happy.
Recommend Org
-
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
-
Microsoft
Open source projects and samples from Microsoft.
-
Google
Google ❤️ Open Source for everyone.
-
Alibaba
Alibaba Open Source for everyone
-
D3
Data-Driven Documents codes.
-
Tencent
China tencent open source team.
from gods.