You can’t do what you’re trying to do: bash arrays are one-dimensional $ declare -A PERSONS $ declare -A PERSON $ PERSON[“FNAME”]=’John’ $ PERSON[“LNAME”]=’Andrew’ $ declare -p PERSON declare -A PERSON='([FNAME]=”John” [LNAME]=”Andrew” )’ $ PERSONS[1]=([FNAME]=”John” [LNAME]=”Andrew” ) bash: PERSONS[1]: cannot assign list to array member You can fake multidimensionality by composing a suitable array index … Read more
There is no built-in solution in PowerShell V1 / V2. You will want to use the .NET System.Collections.Specialized.OrderedDictionary: $order = New-Object System.Collections.Specialized.OrderedDictionary $order.Add(“Switzerland”, “Bern”) $order.Add(“Spain”, “Madrid”) $order.Add(“Italy”, “Rome”) $order.Add(“Germany”, “Berlin”) PS> $order Name Value —- —– Switzerland Bern Spain Madrid Italy Rome Germany Berlin In PowerShell V3 you can cast to [ordered]: PS> [ordered]@{“Switzerland”=”Bern”; “Spain”=”Madrid”; … Read more
Hashtable is the older class, and its use is generally discouraged. Perhaps they saw the need for a null key, and more importantly – null values, and added it in the HashMap implementation. HashMap is newer, and has more advanced capabilities, which are basically just an improvement on the Hashtable functionality. When HashMap was created, … Read more
No need to reinvent the wheel, use a NavigableMap. Example Code: final NavigableMap<Integer, String> map = new TreeMap<Integer, String>(); map.put(0, “Cry Baby”); map.put(6, “School Time”); map.put(16, “Got a car yet?”); map.put(21, “Tequila anyone?”); map.put(45, “Time to buy a corvette”); System.out.println(map.floorEntry(3).getValue()); System.out.println(map.floorEntry(10).getValue()); System.out.println(map.floorEntry(18).getValue()); Output: Cry Baby School Time Got a car yet?
Prerequisites For this answer I’m going to assume you know how to use pointers, structs, and have a basic understanding of the C language. Also if you don’t know. When talking about the speed of algorithms and data structures you should know the terms: O() = (it’s pronounced “Big-oh”) Big-oh or O() refers to the … Read more
The map has to work out which internal table index to use for any given key, mapping any int value (could be negative) to a value in the range [0, table.length). When table.length is a power of two, that can be done really cheaply – and is, in indexFor: static int indexFor(int h, int length) … Read more
Under the appropriate assumptions on the hash function being used, we can say that hash table lookups take expected O(1) time (assuming you’re using a standard hashing scheme like linear probing or chained hashing). This means that on average, the amount of work that a hash table does to perform a lookup is at most … Read more
ConcurrentHashMap and Hashtable locking mechanism Hashtable is belongs to the Collection framework; ConcurrentHashMap belongs to the Executor framework. Hashtable uses single lock for whole data. ConcurrentHashMap uses multiple locks on segment level (16 by default) instead of object level i.e. whole Map. ConcurrentHashMap locking is applied only for updates. In case of retrievals, it allows … Read more
I’ve asked Josh Bloch, and he informs me that it was a mistake. He used to think, long ago, that there was some value in it, but he since “saw the light”. Clearly JDK maintainers haven’t considered this to be worth backing out later.
I would recommend you to try Google SparseHash (or the C11 version Google SparseHash-c11) and see if it suits your needs. They have a memory efficient implementation as well as one optimized for speed. I did a benchmark a long time ago, it was the best hashtable implementation available in terms of speed (however with … Read more