protected void appendFieldStart(StringBuffer buffer, String fieldName) {
        if (useFieldNames && fieldName != null) {
            buffer.append(fieldName);
            buffer.append(fieldNameValueSeparator);
        }
    }
<p>Append to the <code>toString</code> the field start.</p>

@param buffer  the <code>StringBuffer</code> to populate
@param fieldName  the field name
android/android_framework/base/src/main/java/lang3/builder/ToStringStyle.java