public static void isInstanceOf(Class clazz, Object obj) {
        isInstanceOf(clazz, obj, "");
    }
Assert that the provided object is an instance of the provided class.
<pre class="code">Assert.instanceOf(Foo.class, foo);</pre>
@param clazz the required class
@param obj the object to check
@throws IllegalArgumentException if the object is not an instance of clazz
@see Class#isInstance
src/main/java/org/apache/shiro/lang/util/Assert.java