用列表头实现哈希表链的Java程序
哈希表是一种执行连接数组的数据结构，它是一种将键映射到其值的结构。它使用散列函数来计算键的索引位置，也称为散列码。它将键值对存储在一个桶数组中，从这个桶中，可以很容易地在键的帮助下找到值。为了找到该值，键将被散列，其结果将给出该值所在的位置。
方法：
插入：要在哈希表中插入一个键，一个键将被简单地散列以找到它将要插入的位置，然后，该键将被插入到列表的头部。
DELETION：在哈希函数的帮助下遍历列表直到找到键，然后简单地从列表中删除该键
执行：
Java
// Java program which implement Hash Tables chaining with
// List Heads
import java.util.Scanner;
public class TestHashTables {
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
System.out.println(
"***** Hash Table Implementation *****");
System.out.println("Enter size of hash table");
// create object of hash table
HashTablesExample table
= new HashTablesExample(sc.nextInt());
boolean exit = false;
// Perform HashTable operations
while (!exit) {
System.out.println(
"** Hash Table Operations **");
System.out.println("1. insert ");
System.out.println("2. remove");
System.out.println("3. print hash table");
System.out.println("4. get");
System.out.println("5. clear");
System.out.println("6. size");
int choice = sc.nextInt();
switch (choice) {
case 1:
System.out.println("Enter key and value");
String key = sc.next();
int value = sc.nextInt();
table.insert(key, value);
break;
case 2:
System.out.println("Enter key");
String key2 = sc.next();
table.remove(key2);
System.out.println(
"Removed Successfully...");
break;
case 3:
System.out.println(
"Key-value pairs in the hash table are : ");
table.printHashTable();
break;
case 4:
System.out.println("Enter key");
String key3 = sc.next();
System.out.println("Key = " + key3
+ " Value = "
+ table.get(key3));
break;
case 5:
table.makeEmpty();
System.out.println(
"Hash Table Cleared Successfully..");
break;
case 6:
System.out.println("Size of the table is = "
+ table.getSize());
break;
default:
exit = true;
System.out.println(
"Exited Successfully...");
}
}
sc.close();
}
}
class HashTablesExample {
// class linked hash
class LinkedHash {
String key;
int value;
LinkedHash next;
// constructor of linked hash
LinkedHash(String key, int value)
{
this.key = key;
this.value = value;
this.next = null;
}
}
private int tableSize;
private int size;
private LinkedHash[] table;
// constructor of HashTableExample
public HashTablesExample(int ts)
{
size = 0;
tableSize = ts;
table = new LinkedHash[tableSize];
// initializing the hash table with null values
for (int i = 0; i < tableSize; i++)
table[i] = null;
}
// method to get the number of key-value pairs in the
// hash table
public int getSize() { return size; }
// method to clear the hash table entry
public void makeEmpty()
{
for (int i = 0; i < tableSize; i++)
table[i] = null;
}
// method to get value of a key
public int get(String key)
{
int value = (myhash(key) % tableSize);
if (table[value] == null)
return -1;
else {
LinkedHash current = table[value];
while (current != null
&& !current.key.equals(key)) {
current = current.next;
}
if (current == null) {
return -1;
}
else {
return current.value;
}
}
}
// method to insert a value in a hash table
public void insert(String key, int value)
{
int hash = (myhash(key) % tableSize);
if (table[hash] == null) {
table[hash] = new LinkedHash(key, value);
}
else {
LinkedHash entry = table[hash];
while (entry.next != null
&& !entry.key.equals(key)) {
entry = entry.next;
}
if (entry.key.equals(key)) {
entry.value = value;
}
else {
entry.next = new LinkedHash(key, value);
}
}
size++;
}
// method to remove the value with the specified key
public void remove(String key)
{
int value = (myhash(key) % tableSize);
if (table[value] != null) {
LinkedHash prev = null;
LinkedHash current = table[value];
while (current.next != null
&& !current.key.equals(key)) {
prev = current;
current = current.next;
}
if (current.key.equals(key)) {
if (prev == null) {
table[value] = current.next;
}
else {
prev.next = current.next;
}
size--;
}
}
}
// method which gives a hash value from a given
// specified string
private int myhash(String x)
{
int value = x.hashCode();
value %= tableSize;
if (value < 0) {
value = value + tableSize;
}
return value;
}
// method to print the value of hash table
public void printHashTable()
{
for (int i = 0; i < tableSize; i++) {
LinkedHash current = table[i];
while (current != null) {
System.out.println(
"Value = " + current.value + " "
+ "Key = " + current.key);
current = current.next;
}
}
System.out.println();
}
}输出 ：
插入哈希表
从哈希表中删除
打印哈希表的键值对
从指定的键中获取值
清除哈希表
哈希表的大小