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So I need a 2-dimensional ConcurrentHashMap .
It has to be as blazing fast as possible, as I'm going to be adding to and updating its values extremely frequently. It's in a multithreaded application, hence the choice to use ConcurrentHashMap instead of...
Started by DanM on
, 5 posts
by 5 people.
Answer Snippets (Read the full thread at stackoverflow):
*/ void recordAccess(Int2DMap m) { } /** * This method is invoked whenever() - start) / 1 ); Map map2 = new HashMap....
However it will need that's already in the HashMap.
I find it is faster than using an IntPair as key .
Java HashMap.
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I have a list of files. I would like to scan through and keep a count of the number of files with the same size. the issue is with filesize which is a long, as we know, hashmap will take in only an object and not a primitive. So using new Long(filesize...
Started by zeroin23 on
, 7 posts
by 7 people.
Answer Snippets (Read the full thread at stackoverflow):
Here's the pre-Java 5 version of Cletus' example:
Map count = new HashMap(); for (Iterator.
HashCode() value, and the equals() method say they are equal, your HashMap will not create another entry Collections .
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So, I have a situation where I need to pass in three values into a serial BlockingQueue queue:
(SelectableChannel, ComponentSocketBasis, Integer).
They don't actually need to be hash mapped at all, and to use a HashMap is ridiculous as there will always...
Started by Alex Balashov on
, 5 posts
by 5 people.
Answer Snippets (Read the full thread at stackoverflow):
Why not just create your own generic Pair or Triple classes? Pretty much every Java 5+ project ends of thing a lot, creating a generic pair or tuple now will save you a lot of time, but if this is the only.
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Ask your Facebook Friends
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Here's Pair.java
import java.lang.*; import java.util.*; public class Pair<TYPEA, TYPEB> implements Comparable< Pair<TYPEA, TYPEB> > { protected final TYPEA Key_; protected final TYPEB Value_; public Pair(TYPEA key, TYPEB value) { Key...
Started by Chris Kaminski on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
Totally different method that never gets) { System.out.println("in equals()"); if (o instanceof Pair) { Pair<?, ?> p1 = (Pair<?, ?>) o not print "in equals()" after "....
The method with an additional version that takes a Pair .
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If I have the value "foo", and a hashmap ftw for which ftw.containsValue("foo") returns true , how can I get the corresponding key? Do I have to loop through the hashmap? What is the best way to do that?
Started by Rosarch on
, 8 posts
by 8 people.
Answer Snippets (Read the full thread at stackoverflow):
Yes, you have to loop through the hashmap, unless.
It sounds like the best way is for you));
Then when you have a value, you also have the key .
All the pairs in the hashmap, using map.entrySet().
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I am wondering what is the memory overhead of java HashMap compared to ArrayList?
Update:
I would like to improve the speed for searching for specific values of a big pack (6 Millions+) of identical objects.
Thus, I am thinking about using one or several...
Started by elhoim on
, 12 posts
by 12 people.
Answer Snippets (Read the full thread at stackoverflow):
A map (such as HashMap: based on your comment, I ....
As Jon Skeet noted, these are completely different structures.
There are different instances where you'll need a key/value pair (where you may use a HashMap ) and different nice.
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Let's say I want to put words in a data structure and I want to have constant time lookups to see if the word is in this data structure. All I want to do is to see if the word exists. Would I use a HashMap (containsKey()) for this? HashMap s use key-&...
Started by jbu on
, 7 posts
by 7 people.
Answer Snippets (Read the full thread at stackoverflow):
Even if the objects contained in the collection do not change .
Which is the Set equivalent of HashMap.
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I understand that the String class' hashCode() method is not guarantied to generate unique hash codes for distinct String-s. I see a lot of usage of putting String keys into HashMap-s (using the default String hashCode() method). A lot of this usage could...
Started by Marcus on
, 5 posts
by 5 people.
Answer Snippets (Read the full thread at stackoverflow):
HashMap....
You are talking about hash hashCode (e.g.
That is already in the HashMap if and only if the value returned by hashCode is equal, and the equals method, no, it would not be a bad idea to use a String for a key to a HashMap .
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As made clear in update 3 on this answer , this notation:
var hash = {}; hash[X]
does not actually hash the object X ; it actually just converts X to a string (via .toString() if it's an object, or some other built-in conversions for various primitive...
Started by Claudiu on
, 8 posts
by 8 people.
Answer Snippets (Read the full thread at stackoverflow):
If you were to....
You'd have to store in some internal state couplets of object/value pairs
HashMap = {}; // unique object instance var shape = {}; // unique object instance var map = new HashMap(); map.put(color.
Or DojoX UUID.
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My problem is actually more nuanced than the question suggests, but wanted to keep the header brief.
I have a HashMap<String, File> of File objects as values. The keys are String name fields which are part of the File instances. I need to iterate...
Started by milkplusvellocet on
, 10 posts
by 10 people.
Answer Snippets (Read the full thread at stackoverflow):
If you get in the....
Sort it with Collections.sort() according to your hashmap...
You have a temporary List, then add each pair of data into it.
Unfortunately there is no way of getting data out of a HashMap in any recognizable order.
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