wanted to create a class element in the drawing area, that is equivalent to the
following code. Looks like its not possible.

class Stats<T extends Number> {  
  T[] nums; // array of Number or subclass 
  // Pass the constructor a reference to   
  // an array of type Number or subclass. 
  Stats(T[] o) {  
    nums = o;  
  }  
  // Return type double in all cases. 
  double average() {  
    double sum = 0.0; 
    for(int i=0; i < nums.length; i++)  
      sum += nums[i].doubleValue(); 
    return sum / nums.length; 
  }  
}

tspiva comment:
Our metamodel will not support this type of construct.