Question

I need to instantiate a function passed as a string, and i wrote a wrapper for a “Function” object that let me execute the function after it’s defined.

The wrapper uses the JavaAssist library, using object and method as fields of the wrapper object and a method that let me use the function outside the wrapper class.

My troubles are about the function body syntax, i have a lot of
java.lang.VerifyError: (class: MyClass, method: myMethod signature: (*my signature, unimportant *) Expecting to find *a primitive type* on stack

related to casts on the fly, for example

 Double c = (double) intVariable;

which I solved (not really good solution, but it is working) avoiding those casting and always instantiating variables of the defined type

 Double c = new Double( (String) intVariable.toString() );

Now I have another problem, and it’s driving me crazy: this is the content of the string

Double t2 =  new Double ( (String) parametri.get("pigreco").toString() );
Double t3 = new Double ( (String) (new Integer(2)).toString() );";
Double mysum = t2;
mysum+= t3;
return my sum;

t2.getClass() and t3.getClass() return java.lang.Double
but mysum is the concatenation of t2 and t3, not the arithmetic sum… how come is it possible?

Answer 1

For now I have resolved by providing a

public static Double sommaDouble(Double a, Double b) {
    return a+b;
}

in another class. Im looking for a better solution, and I’d like to understand why the “+” is executed as the concatenate operator by Javaassist’s method