Null 指针异常未在 java 对话中捕获

Question

I'm trying to receive input from a java dialog and I can't seem to catch the NullPointerException when the box is closed, can anyone help?

private static final String DEFAULTNAME = "Player001"; 

public class Player implements Serializable
{
    private String name;
    private int score;

    public Player(String Pname,int Pscore)
    {
         name = Pname;
         score = Pscore;
    }
}

    try
    {
        person = new Player(JOptionPane.showInputDialog("Please enter your name"),0);
    }
    catch(NullPointerException e)
    {
        person = new Player(DEFAULTNAME,0);
    }
    catch(Throwable t)
    {
        person = new Player(DEFAULTNAME,0);
    }

Does anyone have a solution or is there a way of making the dialog unable to close?

Answer 1

You don't "catch" a NPE like you're doing. Get the String from the user, see if it == null, and then if so use the default player name. In pseudo code:

call JOptionPane and get player name
If player name is null
  create new Player with default name
else
  create new Player with the user-entered name.

No need for try/catch here.

Another way to solve it is to let your Player constructor accept a null String and change it to default:

public Player(String Pname,int Pscore)
{
     name = (Pname == null || Pname.trim().isEmpty()) ? DEFAULT_NAME : Pname;
     score = Pscore;
}

Answer 2

you are better off checking the name for invalid values before adding it in

String name = JOptionPane.showInputDialog("Please enter your name");
if(name == null || name.equals(""))name = DEFAULTNAME;
person = new Player(name,0);