public Builder clearStringValue() {
      if (stringValueBuilder_ == null) {
        if (valueCase_ == 1) {
          valueCase_ = 0;
          value_ = null;
          onChanged();
        }
      } else {
        if (valueCase_ == 1) {
          valueCase_ = 0;
          value_ = null;
        }
        stringValueBuilder_.clear();
      }
      return this;
    }
<pre>
A string up to 256 bytes long.
</pre>

<code>.google.devtools.cloudtrace.v2.TruncatableString string_value = 1;</code>
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/AttributeValue.java