# Interface MapChangeListener<K,V>

Type Parameters:
  `K` - the key element type
  `V` - the value element type

All Known Implementing Classes:
  `WeakMapChangeListener`

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 MapChangeListener<K,V>
Interface that receives notifications of changes to an ObservableMap.

Since:
  JavaFX 2.0

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Interface
  Description
  `static class`
  `MapChangeListener.Change<K,V>`
  An elementary change done to an ObservableMap.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `onChanged(MapChangeListener.Change<? extends K, ? extends V> change)`
  Called after a change has been made to an ObservableMap.

- ## Method Details

  - ### onChanged

    void onChanged(MapChangeListener.Change<? extends K, ? extends V> change)
    Called after a change has been made to an ObservableMap. This method is called on every elementary change (put/remove) once. This means, complex changes like keySet().removeAll(Collection) or clear() may result in more than one call of onChanged method.
    Parameters:
      `change` - the change that was made