Understanding the Caching Mechanism of Java String HashCode

What is the caching mechanism of Java String hashcode and how does it work?

String str = "example";
int hashCode = str.hashCode(); // This uses cached hashcode.

In Java, `String` objects cache their hashcode upon first calculation to enhance performance during operations that require hashcode evaluation, such as when stored in hash-based collections like HashMap and HashSet.

public class HashCodeExample {
    public static void main(String[] args) {
        String str = "example";
        System.out.println("String: " + str);
        System.out.println("HashCode: " + str.hashCode()); // First calculation
        System.out.println("HashCode: " + str.hashCode()); // Uses cached value
    }
}

Causes

• When a string is created in Java, its hashcode is computed based on the string's content.
• To prevent repeated computation for the same string, Java caches the hashcode after the first calculation.

Solutions

• Use the `hashCode()` method on `String` objects for optimized performance.
• Take advantage of the cached hashcode to improve performance in collections that rely on hashcode evaluations.

Mistake: Not understanding that hashcode might change if the string is mutated.

Solution: Avoid mutating strings that are used as keys in hash-based collections.

Mistake: Not realizing that string literals are interned, leading to potential confusion with hashcode values.

Solution: Utilize the `intern()` method wisely to avoid unexpected behavior with string hashcodes.