Hope you know what function overloading is. Here are the declarations for overloaded method diff().  This is just to give you a start. Define these functions, test the defined functions from the main with different parameters.
public int diff(int a , int b, int c);
public double diff(double a, double b, double c);
public double diff(int a, double b, double c);
public double diff(double a, int b, double c);



Post your code. If you are stuck somewhere.

PS: Use some IDE like Eclipse or Netbeans  that will save ur time.