hashtable - w3toppers.com

Hashtables and key order

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

Why Hashtable does not allow null keys or values?

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

Chained Hash Tables vs. Open-Addressed Hash Tables

Wikipedia’s article on hash tables gives a distinctly better explanation and overview of different hash table schemes that people have used than I’m able to off the top of my head. In fact you’re probably better off reading that article than asking the question here. 🙂 That said… A chained hash table indexes into an … Read more

Why hashmap lookup is O(1) i.e. constant time?

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

What hashing function does Java use to implement Hashtable class?

When a key is added to or requested from a HashMap in OpenJDK, the flow of execution is the following: The key is transformed into a 32-bit value using the developer-defined hashCode() method. The 32-bit value is then transformed by a second hash function (of which Andrew’s answer contains the source code) into an offset … Read more

How to add hashtable to multidimensional array? Cannot assign values via member-access enumeration

tl;dr Setting a key / property value via member-access enumeration is not supported (see below). Instead, you must obtain the specific object whose .Bücher property you want to modify explicitly: ($Data.BIBs.BIB1 | ? Bücher).Bücher += @{ BuchName=”neues Buch”; Autor=”Johann Doe” } Note: This assumes that: only one element of array $Data.BIBs.BIB1 has a .Bücher property … Read more

Hashtable key within integer interval

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?

What is a hash table and how do you make it in C? [closed]

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

Why does HashMap require that the initial capacity be a power of two?

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

ConcurrentHashMap and Hashtable in Java [duplicate]

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