public ConfigureHadoop withKeyValue(ConfigFile file, String key, String value) {
      String arg = "";

      switch (file) {
      case Site: arg = "-s"; break;
      case Default: arg = "-d"; break;
      case Core: arg = "-c"; break;
      case Hdfs: arg = "-h"; break;
      case Mapred: arg = "-m"; break;
      }

      args.add(arg);
      args.add(key + "=" + value);
      return this;
    }
Specify a key-value pair to merge with Hadoop's default configuration.
@param file The config file to merge with.
@param key The config key.
@param value The config value.
@return A reference to this updated object so that method calls can be chained
        together.
aws-java-sdk-emr/src/main/java/com/amazonaws/services/elasticmapreduce/util/BootstrapActions.java