Edit a local variable inside java lambda

Question

I need to change a local variable inside a lambda event handler in javafx.

SerialPort comPorts[] = SerialPort.getCommPorts();
MenuItem[] portsItems = new MenuItem[10];
int q=0;
   for (SerialPort port : comPorts) {
       portsItems[q] = new MenuItem(port.getSystemPortName());
       portsItems[q].setOnAction(actionEvent -> {
               portNum = q;
               connect.setDisable(false);
       });
       comPortsMenu.getItems().add(portsItems[q]);
   }

The problem is I need to increment q in each loop, but I can't do that because q must be final or effectively final to be used inside a lambda.

Answer 1

I think you are looking for something like

for (SerialPort port : comPorts) {
    portsItems[q] = new MenuItem(port.getSystemPortName());
    int portNumber = q ; // effectively final
    portsItems[q].setOnAction(actionEvent -> {
        portNum = portNumber;
        connect.setDisable(false);
    });
    comPortsMenu.getItems().add(portsItems[q]);

    // increment:
    q++ ;
}