public static boolean isNumeric(PositionedByteRange src) {
    byte x = (-1 == Integer.signum(src.peek()) ? DESCENDING : ASCENDING).apply(src.peek());
    return x >= NEG_INF && x <= NAN;
  }
Return true when the next encoded value in {@code src} uses Numeric encoding, false otherwise.
{@code NaN}, {@code +/-Inf} are valid Numeric values.
hbase-common/src/main/java/org/apache/hadoop/hbase/util/OrderedBytes.java