Refactor: use a compiled pattern for skin hash validation

[TheMeinerLP]

Using Pattern.compile() vs matches() for Regular Expressions in Java

This PR optimizes the memory usage for reset pattern in Java.

Why Pattern.compile() is Preferred Over matches()

When working with regular expressions in Java, using Pattern.compile() is significantly more efficient than matches() for several reasons:

1. Performance Optimization: matches() recompiles the regex pattern on each call, while Pattern.compile() only compiles it once.

2. Memory Efficiency: Precompiled patterns reduce memory usage and garbage collection overhead.

3. Reusability: A compiled pattern can be reused across multiple operations.

According to the Java documentation, String.matches() internally creates a new Pattern object each time it's called.

// Inefficient - pattern recompiled on each iteration
for (String s : strings) {
    boolean r = s.matches("regex");
}

// Efficient - pattern compiled once
Pattern pattern = Pattern.compile("regex");
for (String s : strings) {
    boolean r = pattern.matcher(s).matches();
}