title: polymorphism and interfaces
body: <p>if i have two classes x and y, both extend class w. and x implementing interface z. if i have methods doSomething(w object) and doSomething(x object), what would happen if i call doSomething(x)?</p>
  
  <p>edit:
  im implementing this on java, more specifically on android.
  im asking this because some classes which implement a specific interface mostly does the same thing when doSomething() is called. but there are special cases which i would like to single out.</p>