public void putClass(String className, Class<?> clazz) {
            final Class<?> duplicatedClass = this.classCache.putIfAbsent(className, clazz);
            if (duplicatedClass != null) {
                if (logger.isWarnEnabled()) {
                    logger.warn("duplicated pluginClass {}", className);
                }
            }
        }
@author Woonduk Kang(emeroad)
@author jaehong.kim
agent-module/profiler/src/main/java/com/navercorp/pinpoint/profiler/instrument/classloading/PlainClassLoaderHandler.java