Update XMaterial.java

[WI5E]

Code improvements

[CryptoMorin]

Nice! Some micro optimizations that I've missed.
But in here:
return mat == null ? null : mat.name().endsWith("S") ? valueOf(name) : mat;
mat will never return null. Is there any reason you added the null check? Or is it just a "just in case" thing?

Also I don't understand the concept of saving enum values().

[WI5E]

• mat could potentially return null because XMaterial::requestOldXMaterial has the possibility of returning null
• When calling Enum#values it will create a new array each time. If you're going to be executing the call multiple times, cache it once and use it.