RTEditor/src/main/java/com/onegravity/rteditor/converter/tagsoup/HTMLWriter.java
public void forceNSDecl(String uri, String prefix) {
        setPrefix(uri, prefix);
        forceNSDecl(uri);
    }
public void forceNSDecl(String uri, String prefix) {
        setPrefix(uri, prefix);
        forceNSDecl(uri);
    }
Force a Namespace declaration with a preferred prefix.
<p>
<p>
This is a convenience method that invokes {@link #setPrefix setPrefix}
then {@link #forceNSDecl(java.lang.String) forceNSDecl}.
</p>

@param uri    The Namespace URI to declare on the root element.
@param prefix The preferred prefix for the Namespace, or "" for the default
Namespace.
@see #setPrefix
@see #forceNSDecl(java.lang.String)