static boolean isVar(final String name) {
			return !name.isEmpty() && name.charAt(0) == VAR_PREFIX;
		}
@param name the name of the variable
@throws NullPointerException if the given {@code name} is {@code null}
@throws IllegalArgumentException if the given {@code name} is not a
        valid Java identifier
jenetics.ext/src/main/java/io/jenetics/ext/rewriting/TreePattern.java