public PluginLock getPluginLock(String jarFile) {
            final PluginLock exist = this.pluginLock.get(jarFile);
            if (exist != null) {
                return exist;
            }

            final PluginLock newPluginLock = new PluginLock();
            final PluginLock old = this.pluginLock.putIfAbsent(jarFile, newPluginLock);
            if (old != null) {
                return old;
            }
            return newPluginLock;
        }
@author Woonduk Kang(emeroad)
@author jaehong.kim
agent-module/profiler/src/main/java/com/navercorp/pinpoint/profiler/instrument/classloading/PlainClassLoaderHandler.java