Question

I think the sunject’s pretty self-explanatory. I use JDK 1.6.0 update 26, and created a new project with just one line to confirm this:

Boolean.class.newInstance();

and it throws the following:

Exception in thread "main" java.lang.InstantiationException: java.lang.Boolean
    at java.lang.Class.newInstance0(Class.java:340)
    at java.lang.Class.newInstance(Class.java:308)

Does it suppose to fail? If so, why?

Answer 1

Given a class you can find out what it needs to be constructed:

Class cl = // initialize somehow
// get all constructors for class
Constructor[] constructors = cl.getConstructors(); 

 // for each constructor
for(Constructor c : constructors)
{
     // if there is a zero-parameter constructor
    if(c.getParameterTypes().length == 0)
    {
        // then we can safely create a constructor for it
        cl.newInstance(); 
    }
}