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Message:

Is this really synchronized?

Posted by Adam on 02 Oct 1998, 1:09 PM

This is a snippet from the example of synchronizing by
marking critical sections.

public void setColor(int r, int g, int b) {
checkRGBVals(r, g, b);
synchronized (this) {
this.r = r;
this.g = g;
this.b = b;
}
}
private static void checkRGBVals(int r, int g, int b) {
if (r < 0 || r > 255 || g < 0 || g > 255 ||
b < 0 || b > 255) {
throw new IllegalArgumentException();
}
}

This method (setColor) requires reading of the r,g, and b
instance variables to pass them to the class method checkRGBVals. But, unless I'm missing something (it's 4:00 on a Friday so that's possible), this method isn't synchronized with itself. If two threads called this at once, on could be reading the data to call checkRGBVals and one could be writing to it.

right??

shouldn't the call to checkRGBVals be inside the synchronize block too?

Adam

• Each thread has its own stack Bill Venners 18 Oct 1998, 9:44 AM (0)