How to get fully qualified name of parameter value in a method

I have to get the fully qualified name of the method paramter.

For example :

public void display(Custom1 a,Custom2 b){
    String x=a.getValue();
    String y=b.getValue();
}

here Custom1,Custom2 are in com.test.resource so i need to get the value like

com.test.resource.Custom1

I am in need of this in my eclipse plugin.. I used IMethod.getParameterTypes(); .The result is like

QCustom1; how can i get the fully qualified name of the method parameter?

String[] parameterNames = iMethod.getParameterNames();                  
ILocalVariable[] parameterTypes = currentmethod.getMethod().getParameters();                
 for (int j=0; j<parameterNames.length; ++j) {          
        System.out.println("parameter name:"+parameterNames[j]);
        System.out.println("parameter type:"+parameterTypes[j].);
    }

please provide some ideas... thanks in advance.