public static void isAssignable(Class superType, Class subType) {
        isAssignable(superType, subType, "");
    }
Assert that <code>superType.isAssignableFrom(subType)</code> is <code>true</code>.
<pre class="code">Assert.isAssignable(Number.class, myClass);</pre>

@param superType the super type to check
@param subType   the sub type to check
@throws IllegalArgumentException if the classes are not assignable
lang/src/main/java/org/apache/shiro/lang/util/Assert.java