P6-P15: init

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

P12.java

@@ -0,0 +1,43 @@
+import java.beans.PropertyChangeListener;
+import java.beans.PropertyChangeSupport;
+
+public class P12 {
+    private String name;
+    private int age;
+    private PropertyChangeSupport propertyChangeSupport;
+
+    public P12() {
+        propertyChangeSupport = new PropertyChangeSupport(this);
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        String oldName = this.name;
+        this.name = name;
+        propertyChangeSupport.firePropertyChange("name", oldName, name);
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        if (age < 0) {
+            throw new IllegalArgumentException("Age cannot be negative");
+        }
+        int oldAge = this.age;
+        this.age = age;
+        propertyChangeSupport.firePropertyChange("age", oldAge, age);
+    }
+
+    public void addPropertyChangeListener(PropertyChangeListener listener) {
+        propertyChangeSupport.addPropertyChangeListener(listener);
+    }
+
+    public void removePropertyChangeListener(PropertyChangeListener listener) {
+        propertyChangeSupport.removePropertyChangeListener(listener);
+    }
+}