no. unsetting a variable would be assigning null, false or 0 to it. you are talking about casting a variable, that means changing it's type. that's not possible in java, it's a strictly typed language.

but there is help: if you're only using the generate() function from the classes you mentioned, you could use the interface instead: AudioSignal.

basically an interface is a common set of functions that a class can declare to have (implement). that way you can interact with objects of different types in a common way. in your example that would mean that you would have your variable be of type AudioSignal. since both SineWave and SawWave implement AudioSignal the variable can house both these types of objects with the limitation, that you can only call the functions defined by the interface (see link above).

AudioSignal mySignal = new SignWave();
// do smth here ...
mySignal = new SawWave();
// ...

F

right, that will work too.