@java.lang.Override
  public boolean hasDisplayName() {
    return ((bitField0_ & 0x00000001) != 0);
  }
<pre>
Required. A description of the span's operation (up to 128 bytes).
Cloud Trace displays the description in the
Cloud console.
For example, the display name can be a qualified method name or a file name
and a line number where the operation is called. A best practice is to use
the same display name within an application and at the same call point.
This makes it easier to correlate spans in different traces.
</pre>

<code>
.google.devtools.cloudtrace.v2.TruncatableString display_name = 4 [(.google.api.field_behavior) = REQUIRED];
</code>

@return Whether the displayName field is set.
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java