Uso e exemplo do método hashCode() de String em Java

Java String (String) Methods

O método hashCode() de String em Java retorna o código hash da string.

A sintaxe do método hashCode() de String é:

string.hashCode()

Aqui, string é um objeto da classe String.

Parâmetro hashCode()

• Sem nenhum parâmetro

Retorna o valor de hashCode()

• Return the hash code of the string, which is an int value
  

The hash code is calculated using the following formula:

s[0]*31(n-1)　+　s[1]*31(n-2)　+　...　+　s[n-1]

where

• s[0] is the first element of the string s, s[1is the second element, and so on.

• n - is the length of the string

Example: Java string hashCode()

class Main {
　　public static void main(String[] args) {
　　　　String str1　= "Java";
　　　　String str2　= "Java Programming";
　　　　String str3　= "";
　　　　System.out.println(str1.hashCode());　//　2301506
　　　　System.out.println(str2.hashCode());　//　1377009627
　　　　//　hash code of empty string is 0
　　　　System.out.println(str3.hashCode());　//　0
　　}
}

Hash code is a number generated from any object (memory address of the object), not just strings. This number is used to store quickly in hash tables/Retrieve object.

For two strings to be equal, their hash codes must also be equal.

Java String (String) Methods