public void println(Object o) {
        if (duplicate)
            other.println(o);
        stringList.add(o.toString());
    }
Copied from org.slfj.helpers.
 
Currently it is not possible to use test-jar from tests running on the module-path.

@author ceki
slf4j-api/src/test/java/org/slf4j/helpers/StringPrintStream.java