Commons Lang、StandardToStringStyle#setSummaryObjectStartText

import org.apache.commons.lang.builder.StandardToStringStyle;

public class C2009081000 {
    public static void main(String[] args) {
        StandardToStringStyle x = new StandardToStringStyle();
        System.out.println(x.getSummaryObjectStartText());

        x.setSummaryObjectStartText("[");
        System.out.println(x.getSummaryObjectStartText());
    }
}

で、

<
[