Re: Avoiding NPEs caused by indirect call

On 3 ???, 19:45, Lew <com.lewscanon@lew> wrote:


Hi Lew,

There is not much sense in stack trace, it's classic problem, i'm only
looking for the best solution. If stack really matters here's slightly
improved example that you can even run yourself and stack trace:

package test;

import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;

public class Model extends AbstractModel {
    private final PropertyChangeSupport propertyChangeSupport;

    public Model (Object source) {
        propertyChangeSupport = new PropertyChangeSupport(source);
    }

    @Override
    public void addPropertyChangeListener(PropertyChangeListener
listener) {
        propertyChangeSupport.addPropertyChangeListener(listener);
    }

    @Override
    public void firePropertyChange(String propertyName, Object
oldValue, Object newValue) {
        propertyChangeSupport.firePropertyChange(propertyName,
oldValue, newValue);
    }

    public static void main(String[] args) {
    new Model(new Object());
    }
}

abstract class AbstractModel {
    public AbstractModel() {
    indirectCall();
    }

    private void indirectCall() {
    setSomeValue(new Integer(1));
    }

    public void setSomeValue(Integer value) {
        firePropertyChange("someProperty", null, value);
    }

    public void addPropertyChangeListener(PropertyChangeListener
listener) {
    // some code
    }

    protected void firePropertyChange(String propertyName, Object
oldValue, Object newValue) {
        // some code
    }
}