Unlocking the Power of Hash Codes in Java

A Hash Code: More Than Just a Number

A hash code is a unique numerical representation of an object’s memory address. It’s not limited to strings; any object can have a hash code. This number serves as a key to store and retrieve objects quickly in a hashtable.

The Syntax of hashCode()

The hashCode() method is a part of the String class, and its syntax is simple:

int hashCode()

This method takes no parameters and returns an integer value representing the hash code of the string.

The Hash Code Formula

But how is this hash code computed? The formula is based on the string’s characters and length:

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

Here, s[0] is the first element of the string, s[1] is the second element, and so on, while n is the length of the string.

A Practical Example in Java

Let’s see how this works in practice. Consider two strings: “hello” and “hello world”. Using the hashCode() method, we can compute their hash codes:

String str1 = "hello";
String str2 = "hello world";

int hashCode1 = str1.hashCode();
int hashCode2 = str2.hashCode();

System.out.println("Hash code of 'hello': " + hashCode1);
System.out.println("Hash code of 'hello world': " + hashCode2);

The result? Two identical strings will always have the same hash code.

The Importance of Hash Code Equality

It’s crucial to note that for two strings to be considered equal, their hash codes must also be equal. This fundamental principle has far-reaching implications in Java programming.

Beyond Strings: Exploring Object Hash Codes

Hash codes aren’t limited to strings. In fact, any object can have a hash code. To learn more about object hash codes and their applications, explore the world of Java Object hashCode().

• Discover how objects can override the default hashCode() method to provide a custom implementation.
• Learn about the importance of hash code equality in object comparison.
• Explore the various use cases of object hash codes in Java programming.