private void addModifier0(Map<String, ClassFileTransformer> registry, ClassFileTransformer transformer, String className) {
        final String classInternalName = JavaAssistUtils.javaNameToJvmName(className);
        final ClassFileTransformer old = registry.put(classInternalName, transformer);
        if (old != null) {
            throw new IllegalStateException("Transformer already exist. className:" + classInternalName + " new:" + transformer.getClass() + " old:" + old.getClass());
        }
    }
@author emeroad
@author netspider
@author hyungil.jeong
@author Minwoo Jung
@author jaehong.kim
agent-module/profiler/src/main/java/com/navercorp/pinpoint/profiler/instrument/transformer/DefaultTransformerRegistry.java