输出两条打印结果，不理解，哪个大神给分析下原因

import org.apache.log4j.Logger;

public class InnerClassLogger {
    static Logger loggerA = Logger.getLogger(InnerClassLogger.class);

    public static void main(String[] args) {
        loggerA.info(new Object(){
            @Override
            public String toString(){
                loggerA.info("loggerB");
                return "";
            }
        });
    }
}

输出：

0    [main] INFO  InnerClassLogger  - loggerB
0    [main] INFO  InnerClassLogger  - loggerB