opendap/src/main/java/opendap/dap/DGrid.java
public void externalize(DataOutputStream sink) throws IOException {
        arrayVar.externalize(sink);
        for (Enumeration e = mapVars.elements(); e.hasMoreElements();) {
            ClientIO bt = (ClientIO) e.nextElement();
            bt.externalize(sink);
        }
    }
public void externalize(DataOutputStream sink) throws IOException {
        arrayVar.externalize(sink);
        for (Enumeration e = mapVars.elements(); e.hasMoreElements();) {
            ClientIO bt = (ClientIO) e.nextElement();
            bt.externalize(sink);
        }
    }
Writes data to a <code>DataOutputStream</code>. This method is used
primarily by GUI clients which need to download OPeNDAP data, manipulate
it, and then re-save it as a binary file.

@param sink a <code>DataOutputStream</code> to write to.
@throws IOException thrown on any <code>OutputStream</code>
exception.