How to I avoid getting Null Pointer Deference after typing while using getScaledInstance?

Question

To keep it short here is my objective:

to get the photo scale to the jPanel. the best
it could can switch photos at the same time. (I'm using jLabels to get icon)

ps:

I might need to add watermark to the photo so it may be best that you can help me too. Thank You.

BufferedImage img = null;
try {
    img = ImageIO.read(new File("strawberry.jpg"));
} catch (IOException e) {
    e.printStackTrace();
}
Image dimg = img.getScaledInstance(jPanel.getWidth(), jPanel.getHeight(),Image.SCALE_SMOOTH);

can i know is this error talking about:

null pointer deference

See [What is a stack trace, and how can I use it to debug my application errors?](http://stackoverflow.com/q/3988788/418556) & [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/q/218384/418556) — Andrew Thompson, Oct 11 '20 at 07:55
It is not a "deference" . It is a "dereference". Different words. Different spellings. Different meanings. (https://www.lexico.com/definition/dereference) — Stephen C, Oct 11 '20 at 07:57

score 3 · Accepted Answer · answered Sep 19 '20 at 08:57

Your exception handling is the problem.

Your exception handler says:

If a problem occurs, print some (but not all) debug info about it to standard error, and then keep on going with the code.

That is rarely the right move.

The best way to handle an exception is to actually handle it. Logging it isn't handling it.

If you can't handle it (and in this case, hey, how do you 'handle' a crucial file not being there? - You don't, that's not reasonable. Nobody expects you to write code to deal with half of your class files having been deleted either, right?) - then the right alternative is to just throw it onwards - add throws to your method. And if you can't do that, the right 'uhhh I dunno' answer is this:

} (catch IOException e) {
    throw new RuntimeException("unhandled", e);
}

and then the NPE would never have happened. Instead, you get proper info on the actual problem here, which is that strawberry.jpg is not in the current working directory of the JVM process.

To get to the solution to your actual problem: If you have static resources, such as an image of a strawberry for your user interface, put then where your class files end up and use YourClass.class.getResource("strawberry.jpg") to get at them; this uses the same mechanism java uses to find the class files of your app, i.e. it will even get them from within your jar files and such, and avoids any issues with current working directories.

How would using ImageIcon instead solve the problem of the image file being missing? — rzwitserloot, Sep 19 '20 at 11:03

How to I avoid getting Null Pointer Deference after typing while using getScaledInstance?

1 Answers1