public static boolean isInnerClass(Class<?> cls) {
        return cls != null && cls.getEnclosingClass() != null;
    }
<p>Is the specified class an inner class or static nested class.</p>

@param cls  the class to check, may be null
@return {@code true} if the class is an inner or static nested class,
 false if not or {@code null}
android/android_framework/base/src/main/java/lang3/ClassUtils.java