Why PropertyDescriptor(String, Class) constructor uses isFieldName() as the getter name?

I would expect the constructor to test for both getFieldName() and isFieldName() getters. Why is IS_PREFIX the default prefix?

Source code : http://ift.tt/1OHxATe

I use Java 1.8.0_31_b13.

How I use it:

class Foo { String bar; String getBar(){} void setBar(String b){} }
...
new PropertyDescriptor("bar", Foo.class); // fails because isBar is undefined

Demo : http://ift.tt/1UI9wXf