public static void notNull(Object object, String message) {
        if (object == null) {
            throw new IllegalArgumentException(message);
        }
    }
Assert that an object is not {@code null} .
<pre class="code">Assert.notNull(clazz, "The class must not be null");</pre>

@param object  the object to check
@param message the exception message to use if the assertion fails
@throws IllegalArgumentException if the object is {@code null}
src/main/java/spark/utils/Assert.java