Csharp/C Sharp/Collections Data Structure/Hashtable
Содержание
- 1 Add value to Hashtable and loop through the value key pairs
- 2 Compares the efficiency of the hash map implementation with the tree map
- 3 Demonstrate Hashtable
- 4 Enumerating a hash table collection
- 5 Get IDictionaryEnumerator enumerator from Hashtable
- 6 illustrates the use of a Hashtable
- 7 illustrates the use of the Hashtable methods
- 8 Implement GetHashCode method and store it in a hashtable
Add value to Hashtable and loop through the value key pairs
<source lang="csharp"> using System; using System.Collections; public class HashPut {
public static void Main( ) {
String[] identifiers ={"A","B","C","D","E","F","G","H","I","J","K","L"};
String[] types = {"1","2","3","4","5","6","7","8","9","10","11","12"};
Hashtable table = new Hashtable(23);
for(int i = 0; i < identifiers.Length; i++)
table.Add(identifiers[i], types[i]);
Console.WriteLine("The value of F is {0}",table["F"]);
Console.WriteLine("The keys are:");
foreach (DictionaryEntry entry in table)
Console.Write("{0} ", entry.Key);
}
}
</source>
Compares the efficiency of the hash map implementation with the tree map
<source lang="csharp"> using System; using System.Collections; public class CompareMaps {
public const int MAX = 50000000;
public static String time(IDictionary map) {
Object value = null;
long starttime = Environment.TickCount;
for (int i = 0; i < MAX; i++) {
value = map[i];
}
long stoptime = Environment.TickCount;
return value + " took " + (stoptime - starttime);
}
public static void Main(String[] args) {
int SIZE = 1000;
IDictionary hash = new Hashtable(2*SIZE);
IDictionary tree = new SortedList();
Random random = new Random();
int i = random.Next(5000000);
for (int j = 0; j < SIZE; j++) {
if(!hash.Contains(i))
hash.Add(i, i);
if(!tree.Contains(i))
tree.Add(i, i);
}
Console.WriteLine("Hash for {0}", time(hash));
Console.WriteLine("Tree for {0}", time(tree));
}
}
</source>
Demonstrate Hashtable
<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852
- /
// Demonstrate Hashtable.
using System; using System.Collections;
public class HashtableDemo {
public static void Main() {
// Create a hash table.
Hashtable ht = new Hashtable();
// Add elements to the table
ht.Add("house", "Dwelling");
ht.Add("car", "Means of transport");
ht.Add("book", "Collection of printed words");
ht.Add("apple", "Edible fruit");
// Can also add by using the indexer.
ht["tractor"] = "farm implement";
// Get a collection of the keys.
ICollection c = ht.Keys;
// Use the keys to obtain the values.
foreach(string str in c)
Console.WriteLine(str + ": " + ht[str]);
}
}
</source>
Enumerating a hash table collection
<source lang="csharp"> using System; using System.Collections; class Test{
public static void Main() {
Hashtable ht = new Hashtable(10);
// Add strings to the hashtable associated with a
// key value (integer).
ht.Add( 100, "Z");
ht.Add( 200, "A");
ht.Add( 300, "B");
ht.Add( 400, "S");
ht.Add( 500, "G");
foreach ( DictionaryEntry de in ht ) {
Console.WriteLine( "Entry Key {0} Value {1}", de.Key, de.Value );
}
}
}
</source>
Get IDictionaryEnumerator enumerator from Hashtable
<source lang="csharp">
using System; using System.Collections; public class Starter {
public static void Main() {
Hashtable zHash = new Hashtable();
zHash.Add("one", 1);
zHash.Add("two", 2);
zHash.Add("three", 3);
zHash.Add("four", 4);
IDictionaryEnumerator e = zHash.GetEnumerator();
while (e.MoveNext()) {
Console.WriteLine(
"{0} {1}",
e.Key, e.Value);
}
}
}
</source>
illustrates the use of a Hashtable
<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110
- /
/*
Example11_6.cs illustrates the use of a Hashtable
- /
using System; using System.Collections; public class Example11_6 {
public static void Main()
{
// create a Hashtable object
Hashtable myHashtable = new Hashtable();
// add elements containing US state abbreviations and state
// names to myHashtable using the Add() method
myHashtable.Add("AL", "Alabama");
myHashtable.Add("CA", "California");
myHashtable.Add("FL", "Florida");
myHashtable.Add("NY", "New York");
myHashtable.Add("WY", "Wyoming");
// display the Count property
Console.WriteLine("myHashtable.Count = " + myHashtable.Count);
// lookup the state name for "CA"
string myState = (string) myHashtable["CA"];
Console.WriteLine("myState = " + myState);
// display the keys for myHashtable using the Keys property
foreach (string myKey in myHashtable.Keys)
{
Console.WriteLine("myKey = " + myKey);
}
// display the values for myHashtable using the Values property
foreach(string myValue in myHashtable.Values)
{
Console.WriteLine("myValue = " + myValue);
}
}
}
</source>
illustrates the use of the Hashtable methods
<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110
- /
/*
Example11_7.cs illustrates the use of the Hashtable methods
- /
using System; using System.Collections; public class Example11_7 {
public static void Main()
{
// create a Hashtable object
Hashtable myHashtable = new Hashtable();
// add elements containing US state abbreviations and state
// names to myHashtable using the Add() method
myHashtable.Add("AL", "Alabama");
myHashtable.Add("CA", "California");
myHashtable.Add("FL", "Florida");
myHashtable.Add("NY", "New York");
myHashtable.Add("WY", "Wyoming");
// display the keys for myHashtable using the Keys property
foreach (string myKey in myHashtable.Keys)
{
Console.WriteLine("myKey = " + myKey);
}
// display the values for myHashtable using the Values property
foreach(string myValue in myHashtable.Values)
{
Console.WriteLine("myValue = " + myValue);
}
// use the ContainsKey() method to check if myHashtable
// contains the key "FL"
if (myHashtable.ContainsKey("FL"))
{
Console.WriteLine("myHashtable contains the key FL");
}
// use the ContainsValue() method to check if myHashtable
// contains the value "Florida"
if (myHashtable.ContainsValue("Florida"))
{
Console.WriteLine("myHashtable contains the value Florida");
}
// use the Remove() method to remove FL from myHashtable
Console.WriteLine("Removing FL from myHashtable");
myHashtable.Remove("FL");
// get the number of elements in myHashtable using the Count
// property
int count = myHashtable.Count;
// copy the keys from myHashtable into an array using
// the CopyTo() method and then display the array contents
Console.WriteLine("Copying keys to myKeys array");
string[] myKeys = new string[count];
myHashtable.Keys.CopyTo(myKeys, 0);
for (int counter = 0; counter < myKeys.Length; counter++)
{
Console.WriteLine("myKeys[" + counter + "] = " +
myKeys[counter]);
}
// copy the values from myHashtable into an array using
// the CopyTo() method and then display the array contents
Console.WriteLine("Copying values to myValues array");
string[] myValues = new string[count];
myHashtable.Values.CopyTo(myValues, 0);
for (int counter = 0; counter < myValues.Length; counter++)
{
Console.WriteLine("myValues[" + counter + "] = " +
myValues[counter]);
}
}
}
</source>
Implement GetHashCode method and store it in a hashtable
<source lang="csharp"> using System; using System.Collections; public class GoodCompare {
public static void Main() {
Name president = new Name ("A", "B");
Name first = new Name ("C", "D");
Hashtable m = new Hashtable();
m.Add(president, "first");
Console.WriteLine(m.Contains(first));
Console.WriteLine(m[first]);
}
}
public class Name {
protected String first;
protected char initial;
protected String last;
public Name(String f, String l) {
first = f;
last = l;
}
public Name(String f, char i, String l) : this(f,l) {
initial = i;
}
public override String ToString() {
if (initial == "\u0000")
return first + " " + last;
else
return first + " " + initial + " " + last;
}
public override bool Equals(Object o) {
if (!(o is Name))
return false;
Name name = (Name)o;
return first == name.first && initial == name.initial
&& last == name.last;
}
public override int GetHashCode() {
return first.GetHashCode() + (int)initial
+ last.GetHashCode();
}
}
</source>
