code: public final String getProperty(String key, String defaultValue)
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(this, tc, "getProperty", new Object[] { "Key=" + key, "Default=" + defaultValue });
  
          String fullKey = MessageStoreConstants.STANDARD_PROPERTY_PREFIX + key;
  
          // consult custom properties first
          String value = (String) _customProperties.get(fullKey);
          //TODO in a gradle unit test environment, I can't get RuntimeInfo to properly initialize (NoClassDefFoundError).
          //however, it also appears that RuntimeInfo.getProperty is not properly implemented on Liberty anyway, it always returns null
          //so commenting it out here makes no difference and allows the tests to pass. Needs fixing properly.
  //        if (null == value)
  //        {
  //            value = RuntimeInfo.getProperty(fullKey);
  //        }
          if (null == value)
          {
              // If still nothing then go to system proprties
              value = System.getProperty(fullKey);
          }
          if (null == value)
          {
              // if still nothing, then use the supplied default.
              value = defaultValue;
          }
          else
          {
              // If the value used differs from the default, issue a confirmation
              // message for serviceability reasons
              if (!value.equals(defaultValue))
              {
                  Runtime.changedPropertyValue(fullKey, value);
              }
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(this, tc, "getProperty", "return=" + value);
          return value;
      }
docs: Reply property value. Value returned will be from one of
  these sources, in order of search:
  <ul>
  <li>Custom Properties</li>
  <li>SIB Properties</li>
  <li>System Properties</li>
  <li>default supplied</li>
  </ul>
  
  @param key Name of property for which the value is required.
  The standard prefix of "sib.msgstore." will be appended by this
  method and should not form part of the key supplied.
  @param defaultValue Default value to return if no value found.
  @return Property value.