
replace code 
```java
  ExtensionLoader<T> loader = (ExtensionLoader<T>) EXTENSION_LOADERS.get(type);
    if (loader == null) {
        EXTENSION_LOADERS.putIfAbsent(type, new ExtensionLoader<T>(type));
        loader = (ExtensionLoader<T>) EXTENSION_LOADERS.get(type);
    }
  return loader;
```

to

```java
return (ExtensionLoader<T>) EXTENSION_LOADERS.computeIfAbsent(type, k -> new ExtensionLoader<T>(type));
```


/**
     * Replace the existing extension via API
     *
     * @param name  extension name
     * @param clazz extension class
     * @throws IllegalStateException when extension to be placed doesn't exist
     * @deprecated not recommended any longer, and use only when test
     */
    @Deprecated
    public void replaceExtension(String name, Class<?> clazz) {
        getExtensionClasses(); 
        if (!type.isAssignableFrom(clazz)) {
            throw new IllegalStateException("Input type " +
                    clazz + " doesn't implement Extension " + type);
        }
        if (clazz.isInterface()) {
            throw new IllegalStateException("Input type " +
                    clazz + " can't be interface!");
        }
        if (!clazz.isAnnotationPresent(Adaptive.class)) {
            if (StringUtils.isBlank(name)) {
                throw new IllegalStateException("Extension name is blank (Extension " + type + ")!");
            }
            if (!cachedClasses.get().containsKey(name)) {
                throw new IllegalStateException("Extension name " +
                        name + " doesn't exist (Extension " + type + ")!");
            }
            cachedNames.put(clazz, name);
            cachedClasses.get().put(name, clazz);
            cachedInstances.remove(name);