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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 two HashMaps: FOO & BAR.
HashMap FOO is a superset of HashMap BAR.
How do I find out what 'keys' are missing in HashMap BAR (i.e. exists in FOO but not BAR)?
Answer Snippets (Read the full thread at stackoverflow):
Set missing = new HashSet(foo.keySet()); missing.removeAll(bar.keySet());
If you're using google-collections (and realistically I think it should be on the classpath of more or less every non-trivial Java project) it's just:
Set<X> missing = Sets... .
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Hi,
does anyone know of a good library or method of converting the contents of a HashMap to XML and then parsing this to reconstruct the HashMap?
Started by Aly on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
Http://xstream.codehaus.org/
It has a HashMap converter.
The XStream library is what you want.
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Hi,
I have a pretty big (100'000s of entries) HashMap . Now, I need a HashSet containing all the keys from this HashMap . Unfortunately, HashMap only has a keySet() method which returns a Set but not a HashSet .
What would be an efficient way to generate...
Started by Haes on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
MapBackedHashSet extends HashSet { private HashMap theMap; public MapBackedHashSet(HashMap theMap.
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Hi all gurus!
I am facing a problem. I used the following hashmap to store some values
HashMap<String, Object> hm = new HashMap<String, Object>();
The object is another HashMap (yeah, you can say HashMap of HashMap). String is to store book...
Answer Snippets (Read the full thread at stackoverflow):
Maybe you already know them (if they are fixed), otherwise you have to loop over all of them... .
The first thing you need to do is to figure out the unique keys in your second-level map and assign them to columns .
Definitely no built-in function to do this.
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Could anyone please tell important use cases of Identity HashMap?
Started by Thomman on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
In a HashMap....
HashMap creates lots of objects.
This is about 33% faster than HashMap for gets! It probably uses less memory too.
Experience from me:
IdentityHashMap leaves a much smaller memory footprint compared to HashMap.
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I have the following piece of code :
private static HashMap<String, TestObject> labelHash= new HashMap<String, TestObject>(); private static HashMap<String, TestObject> valueHash= new HashMap<String, TestObject>(); private HashMap...
Started by Tiberiu Hajas on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
Are you doing anything with these TestObject s?
HashMap s (and collections in general) store.
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Why HashMap extends AbstractMap and implement Map ? is extending AbstractMap not sufficient, because AbstractMap implements Map?
Started by SomaSekhar on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
The fact that future versions of HashMap ....
HashMap implements Map, and you can rely on that.
I suspect that it was done for "documentation" reasons.
It is redundant.
They originally wrote the HashMap implementation, I don't know.
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Coming from a Java world into a C# one is there a HashMap equivalent? If not what would you recommend?
Started by John on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
Hashtable.
IDictionary interface (which is similar to Java's Map interface).
System.Collections.Generic.Dictionary implements the System.Collections.Generic.
Dictionary is probably the closest.
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Hi All !
I have hashmap and its keys are like "folder/1.txt,folder/2.txt,folder/3.txt" and value has these text files data.
Now i am stucked. I want to sort this list. But it does not let me do it :( Here is my hashmap data type:
HashMap<String, ArrayList...
Answer Snippets (Read the full thread at stackoverflow):
If your hashmap is called h , then try.
I guess that you want the list of keys sorted .
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