Added new namespace JDotNet.Properties II

src/main/java/com/openeggbert/jdotnet/JDotNet/Properties/IVetoablePropertyChangeListener.java

@@ -0,0 +1,8 @@
+package com.openeggbert.jdotnet.JDotNet.Properties;
+
+@FunctionalInterface
+public interface IVetoablePropertyChangeListener<T> {
+    void vetoablePropertyChanged(T oldValue, T newValue) throws PropertyVetoException;
+
+
+}

src/main/java/com/openeggbert/jdotnet/JDotNet/Properties/ObservablePropertyImpl.java

@@ -18,6 +18,7 @@ public class ObservablePropertyImpl<T> extends PropertyImpl<T> implements IObser
 
     private List<Consumer<T>> observers = new ArrayList<>();
     private final List<IPropertyChangeListener<T>> changeListeners = new ArrayList<>();
+    private final List<IVetoablePropertyChangeListener<T>> vetoableChangeListeners = new ArrayList<>();
 
     public ObservablePropertyImpl(IReadOnlyProperty<T> readOnlyPropertyIn, IWriteOnlyProperty<T> writeOnlyPropertyIn) {
         super(readOnlyPropertyIn, writeOnlyPropertyIn);
@@ -35,6 +36,15 @@ public class ObservablePropertyImpl<T> extends PropertyImpl<T> implements IObser
     @Override
     public void set(T valueIn) {
         T oldValue = this.get();
+
+        boolean vetoed = false;
+        if(!vetoableChangeListeners.isEmpty()) {
+             vetoed = notifyVetoableChangeListeners(oldValue, valueIn);
+        }
+        if(vetoed) {
+            //nothing to do
+            return;
+        }
         super.set(valueIn);
         if(!observers.isEmpty()) {
             notifyListeners(valueIn);
@@ -55,6 +65,26 @@ public class ObservablePropertyImpl<T> extends PropertyImpl<T> implements IObser
         }
     }
 
+    /**
+     * Notifies all registered vetoable change listeners of a potential change
+     * from the old value to the new value. If any listener vetoes the change by
+     * throwing a {@code PropertyVetoException}, the method stops further notifications
+     * and returns {@code true}.
+     *
+     * @param oldValue the previous value before the change
+     * @param newValue the proposed new value
+     * @return {@code true} if the change was vetoed by any listener; {@code false} otherwise
+     */
+    private boolean notifyVetoableChangeListeners(T oldValue, T newValue) {
+        for (IVetoablePropertyChangeListener<T> listener : vetoableChangeListeners) {
+            try {
+                listener.vetoablePropertyChanged(oldValue, newValue);
+            } catch (PropertyVetoException e) {
+                return true;
+            }
+        }
+        return false;
+    }
     public void addChangeListener(IPropertyChangeListener<T> changeListener) {
         changeListeners.add(changeListener);
     }
@@ -62,6 +92,13 @@ public class ObservablePropertyImpl<T> extends PropertyImpl<T> implements IObser
     public void removeChangeListener(IPropertyChangeListener<T> changeListener) {
         changeListeners.remove(changeListener);
     }
+    public void addVetoableChangeListener(IVetoablePropertyChangeListener<T> changeListener) {
+        vetoableChangeListeners.add(changeListener);
+    }
+
+    public void removeVetoableChangeListener(IVetoablePropertyChangeListener<T> vetoablePropertyChangeListener) {
+        vetoableChangeListeners.remove(vetoablePropertyChangeListener);
+    }
 
 
     public void addObserver(Consumer<T> listener) {
@@ -73,7 +110,7 @@ public class ObservablePropertyImpl<T> extends PropertyImpl<T> implements IObser
     }
 
     public boolean hasListeners() {
-        return !observers.isEmpty() || !changeListeners.isEmpty();
+        return !observers.isEmpty() || !changeListeners.isEmpty() || !vetoableChangeListeners.isEmpty();
     }
     public boolean hasObservers() {
         return !observers.isEmpty();
@@ -81,5 +118,8 @@ public class ObservablePropertyImpl<T> extends PropertyImpl<T> implements IObser
     public boolean hasChangeListeners() {
         return !changeListeners.isEmpty();
     }
+    public boolean hasVetoableChangeListeners() {
+        return !vetoableChangeListeners.isEmpty();
+    }
 
 }

src/main/java/com/openeggbert/jdotnet/JDotNet/Properties/PropertyVetoException.java

@@ -0,0 +1,9 @@
+package com.openeggbert.jdotnet.JDotNet.Properties;
+
+import com.openeggbert.jdotnet.JDotNet.JDotNetException;
+
+public class PropertyVetoException extends JDotNetException {
+    public PropertyVetoException(String message) {
+        super(message);
+    }
+}