Observer (GRIP API)

Type Parameters:

T - the type of the value to observe

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
public interface Observer<T>
```
Observes changes to the value of an Observable.

- Method Summary
  
  All Methods Instance Methods Abstract Methods
  Modifier and Type Method Description
  
  void onChange(T previous, T current)
  Called when the value of the observable changes.

- Method Detail
  - onChange
```
void onChange(T previous,
              T current)
```
    Called when the value of the observable changes.
    
    Parameters:
    
    previous - the previous value of the observable
    
    current - the current value of the observable