Invalid Method Declaration; Return Type Required


This Java software error message means the return type of a method was not explicitly stated in the method signature.
public class Circle
{
    private double radius;
    public CircleR(double r)
    {
        radius = r;
    }
    public diameter()
    {
       double d = radius * 2;
       return d;
    }
}

There are a few ways to trigger the “invalid method declaration; return type required” error:
  • Forgetting to state the type
  • If the method does not return a value then “void” needs to be stated as the type in the method signature.
  • Constructor names do not need to state type. But if there is an error in the constructor name, then the compiler will treat the constructor as a method without a stated type.