Java.lang.ClassLoader

Question

What's the use of java.lang.ClassLoader.
I write some test code:
public class ClassLoaderDemo {
  public static void main(String[] args) throws Exception {
    Class cls = Integer.class;
    ClassLoader cld = cls.getClassLoader();
    cls = cld.loadClass("java.lang.Integer");
}But it thrown NullPointerException? why?

Answer 1

Because java.lang.Integer is a built-in type which isn't loaded by a standard ClassLoader. Hence it's getClassLoader() returns null. If you substitute
Class cls = ClassLoaderDemo.class;You should get a better resuilt.