How to remove lambda expressions / methods used as listeners?

Question

Java 8 has implemented lambda expressions , which is great. But now consider rewriting this code:

class B implements PropertyChangeListener {
    void listenToA(A a) {
        a.addPropertyChangeListener(this);
    }

    void propertyChange(PropertyChangeEvent evt) {
        switch(evt.getPropertyName()) {
            case "Property1":
                doSomething();
                break;
            case "Property2":
                doSomethingElse();                case "Property1":
                doSomething;
                break;

                break;
    }

    void doSomething() { }
    void doSomethingElse() { }
}

class A {
    final PropertyChangeSupport pcs = new PropertyChangeSupport(this);

    void addPropertyChangeListener(PropertyChangeListener listener) {
        pcs.addPropertyChangeListener(listener);
    }

    void removePropertyChangeListener(PropertyChangeListener listener) {
        pcs.removePropertyChangeListener(listener);
    }
}

With lambda expressions and method references, you no longer have to Bimplement it PropertyChangeListner, as we can write

class B {
    void listenToA(A a) {
        // using method reference
        a.addPropertyChangeListener("Property1", this::doSomething);
        // using lambda expression
        a.addPropertyChangeListener("Property2", e -> doSomethingElse());
    }

    void doSomething(PropertyChangeEvent evt) { }
    void doSomethingElse() { }
}

class A {
    final PropertyChangeSupport pcs = new PropertyChangeSupport(this);

    void addPropertyChangeListener(String name, PropertyChangeListener listener) {
        pcs.addPropertyChangeListener(name, listener);
    }

    void removePropertyChangeListener(String name, PropertyChangeListener listener) {
        pcs.removePropertyChangeListener(name, listener);
    }
}

I think the new code is not only shorter, but also cleaner and more understandable. But after reading the answers here (a duplicate of this , but I think the question and answer are clearer), I see no way to implement a method called stopListening()that will remove the listeners again.

, , . - , , , ?

UPDATE

. Hovercraft Full Of Eels, :

class B {
    void listenToA(A a) {
        a.addPropertyChangeListener("Property1", doSomething);
        a.addPropertyChangeListener("Property2", doSomethingElse);
    }

    final PropertyChangeListener doSomething = evt -> {};
    final PropertyChangeListener doSomethingElse = evt -> {};
}

Answer 1

:

private final PropertyChangeListener myProperty1Listener = this::doSomething;
private final PropertyChangeListener myProperty2Listener = e -> doSomethingElse());

:

// using method reference
a.addPropertyChangeListener( "Property1", myProperty1Listener );
// using lambda expression
a.addPropertyChangeListener( "Property2", myProperty2Listener );

:

a.removePropertyChangeListener( "Property1", myProperty1Listener );
a.removePropertyChangeListener( "Property2", myProperty2Listener );

Answer 2

lambdas . , :

class B {
    private PropertyChangeListener listener1 = this::doSomething;
    private PropertyChangeListener listener2 = e -> doSomethingElse(); 

    void listenToA(A a) {
        // using method reference
        a.addPropertyChangeListener("Property1", listener1);
        // using lambda expression
        a.addPropertyChangeListener("Property2", listener2);
    }

listener1 listener2, .

, PropertyChangeSupport getPropertyChangeListeners(), for, .

class A {
    final PropertyChangeSupport pcs = new PropertyChangeSupport(this);

    void addPropertyChangeListener(String name, PropertyChangeListener listener) {
        pcs.addPropertyChangeListener(name, listener);
    }

    void removePropertyChangeListener(String name, PropertyChangeListener listener) {
        pcs.removePropertyChangeListener(name, listener);
    }

    public void removeAllListeners() {
        for (PropertyChangeListener l : pcs.getPropertyChangeListeners()) {
            pcs.removePropertyChangeListener(l);
        }
    }
}