createReader() example

Programming Questions

alphachap

in Programming Questions • 2 years ago

I tried the createReader() reference example, with no file positions.txt

I thought the try/catch would work, but I get a runtime error: Null Pointer Exception

Can this be fixed?

Maybe the error should be catched earlier at the

reader = createReader("positions.txt");

instruction instead? But how to do that?

positions.txt does not exist or could not be read
processing.app.debug.RunnerException: NullPointerException
at processing.app.Sketch.placeException(Sketch.java:1543)
at processing.app.debug.Runner.findException(Runner.java:582)
at processing.app.debug.Runner.reportException(Runner.java:558)
at processing.app.debug.Runner.exception(Runner.java:498)
at processing.app.debug.EventThread.exceptionEvent(EventThread.java:367)
at processing.app.debug.EventThread.handleEvent(EventThread.java:255)
at processing.app.debug.EventThread.run(EventThread.java:89)
Exception in thread "Animation Thread" java.lang.NullPointerException
at sketch_mar10c.draw(sketch_mar10c.java:30)
at processing.core.PApplet.handleDraw(Unknown Source)
at processing.core.PApplet.run(Unknown Source)
at java.lang.Thread.run(Thread.java:619)

BufferedReader reader;
String line;
void setup() {
// Open the file from the createWriter() example
reader = createReader("positions.txt");
}
void draw() {
try {
    line = reader.readLine(); // <<<<<<<<<<< ERROR
}
catch (IOException e) {
    e.printStackTrace();
    line = null;
}
if (line == null) {
    // Stop reading because of an error or file is empty
    noLoop();
}
else {
    String[] pieces = split(line, TAB);
    int x = int(pieces[0]);
    int y = int(pieces[1]);
    point(x, y);
}
}

Replies(1)

PhiLho

Re: createReader() example

2 years ago

In general, Processing catches exceptions and doesn't expose them to the user. Otherwise, the catch probably should have been on the createReader anyway.
Here, the solution is simple: just check if reader is null before using it.

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