KeyboardFocusManager.java 文件源码

/**
 * Fires a PropertyChangeEvent in response to a change in a bound property.
 * The event will be delivered to all registered PropertyChangeListeners.
 * No event will be delivered if oldValue and newValue are the same.
 *
 * @param propertyName the name of the property that has changed
 * @param oldValue the property's previous value
 * @param newValue the property's new value
 */
protected void firePropertyChange(String propertyName, Object oldValue,
                                  Object newValue)
{
    if (oldValue == newValue) {
        return;
    }
    PropertyChangeSupport changeSupport = this.changeSupport;
    if (changeSupport != null) {
        changeSupport.firePropertyChange(propertyName, oldValue, newValue);
    }
}