Java String hashCode() usage and example

Java String (String) Methods

The Java String hashCode() method returns the hash code of the string.

The syntax of the string.hashCode() method is:

string.hashCode()

Here, string is an object of the String class.

hashCode() parameter

• without any parameters

hashCode() return value

• 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
　　}
}

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

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

Java String (String) Methods