public static TableName valueOf(String namespaceAsString, String qualifierAsString) {
    if (namespaceAsString == null || namespaceAsString.length() < 1) {
      namespaceAsString = NamespaceDescriptor.DEFAULT_NAMESPACE_NAME_STR;
    }

    for (TableName tn : tableCache) {
      if (
        qualifierAsString.equals(tn.getQualifierAsString())
          && namespaceAsString.equals(tn.getNamespaceAsString())
      ) {
        return tn;
      }
    }

    return createTableNameIfNecessary(ByteBuffer.wrap(Bytes.toBytes(namespaceAsString)),
      ByteBuffer.wrap(Bytes.toBytes(qualifierAsString)));
  }
It is used to create table names for old META, and ROOT table. These tables are not really
legal tables. They are not added into the cache.
@return a dummy TableName instance (with no validation) for the passed qualifier
hbase-common/src/main/java/org/apache/hadoop/hbase/TableName.java