public String getSparkProperty(String key, String defaultValue) {
    String val = getSparkProperty(key);
    if (val == null) {
      return defaultValue;
    }
    return val;
  }
This data class holds Spark environment data (Spark properties, JVM properties and etc.)
app/com/linkedin/drelephant/spark/legacydata/SparkEnvironmentData.java