cdm/src/main/java/ucar/unidata/util/Parameter.java
public String getStringValue() {
    if (valueS == null) {
      StringBuilder sbuff = new StringBuilder();
      for (double v : valueD) {
        sbuff.append(v).append(" ");
      }
      valueS = sbuff.toString();
    }
    return valueS;
  }
public String getStringValue() {
    if (valueS == null) {
      StringBuilder sbuff = new StringBuilder();
      for (double v : valueD) {
        sbuff.append(v).append(" ");
      }
      valueS = sbuff.toString();
    }
    return valueS;
  }
Retrieve String value; only call if isString() is true.

@return String if this is a String valued attribute, else null.