The VS Code snippet engine now supports variable transformations. 
Transformations can change the value of a variable before inserting it. 
The format is var_name/regular_expression/format_string/options. 
The sample below is a snippet that creates a public Java class whose name 
is derived from the filename.

  "Public Class": {
    "prefix": "pclass",
    "body": [
      "public class ${1:${TM_FILENAME/(.*)\\.java/${1:/capitalize}/}} {",
      "\tpublic $1 (${2:params}) {",
      "\t\t$0",
      "\t}",
      "}"
    ],
    "description": "New public class"
  }
The new part is this: ${TM_FILENAME/(.*)\\.java/${1:/capitalize}/} and this is what it does:

Resolve the value for TM_FILENAME, for example myClass.java.
Use the regular expression /(.*)\\.java to create a matching group for everything that precedes 
the .java ending, for example myClass.
Take the value of the first matching group, ensure it start with capital letters (/capitalize), 
and insert it (MyClass).