add code removed previously

Author: cecile75

dd-java-agent/agent-otel/otel-shim/src/main/java/datadog/opentelemetry/shim/metrics/OtelMeter.java

@@ -6,14 +6,16 @@
 import io.opentelemetry.api.metrics.LongCounterBuilder;
 import io.opentelemetry.api.metrics.LongUpDownCounterBuilder;
 import io.opentelemetry.api.metrics.Meter;
+import io.opentelemetry.api.metrics.MeterProvider;
 import io.opentelemetry.api.metrics.ObservableMeasurement;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 // https://www.javadoc.io/doc/io.opentelemetry/opentelemetry-api/1.47.0/io/opentelemetry/api/metrics/Meter.html
 public class OtelMeter implements Meter {
   private static final Logger LOGGER = LoggerFactory.getLogger(OtelMeter.class);
-
+  private static final Meter NOOP_METER = MeterProvider.noop().get("noop");
+  private static final String NOOP_INSTRUMENT_NAME = "noop";
   private final String instrumentationScopeName;
   private final String schemaUrl;
   private final String instrumentationVersion;
@@ -76,4 +78,28 @@ public BatchCallback batchCallback(
     LOGGER.info("batchCallback is not yet supported");
     return Meter.super.batchCallback(callback, observableMeasurement, additionalMeasurements);
   }
+
+  private static boolean isInstrumentNameInvalid(String instrumentName) {
+    if ((null == instrumentName)
+        || instrumentName.isEmpty()
+        || instrumentName.length() > 255
+        || !Character.isLetter(instrumentName.charAt(0))
+        || HasAnyInvalidCharacter(instrumentName)) {
+      LOGGER.warn(
+          "Invalid instrument name {}. Instrument names must be ASCII, start with letter, contain only alphanumeric characters, '_', '.', '/', '-' and be max 255 characters.",
+          instrumentName);
+      return true;
+    }
+    return false;
+  }
+
+  private static boolean HasAnyInvalidCharacter(String instrumentName) {
+    for (int i = 1; i < instrumentName.length(); i++) {
+      char c = instrumentName.charAt(i);
+      if (!Character.isLetterOrDigit(c) && c != '_' && c != '.' && c != '/' && c != '-') {
+        return true;
+      }
+    }
+    return false;
+  }
 }