Automatic type conversion?

Processing Beginners
1

The parameters for ellipse() are all of type float (https://processing.org/reference/ellipse_.html). Why does this work when I pass in all ints? Is there type conversion happening in the background? I have been using these 2D shapes for years but never realized that the parameter types are floats.

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  • Java simply upgrades a passed argument to a float if it isn’t already.
  • What Java won’t do is downgrade a double to a float though!
  • So something like this won’t compile: ellipse(56d, 46, 55, 55);.
  • Notice the literal 56 got a d suffix on it, meaning it is of datatype double.
  • The only exception I can remember now where Java can downgrade a primitive datatype is when we use 1 of its composite assignment operators such as +=, /=, ^=, etc.:
    += (add assign) / Reference / Processing.org
int a = 10;
a *= PI;
println(a); // 31 instead of 31.415928
exit();
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I’ve seen this fail in constructors sometimes though. If you declare float in a constructor and pass an int it will often prompt you to pass a float.

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Prompt? Who exactly does it? Never seen it and it has never failed on me! :confused:

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image

this is in a method, but it does it with my slider and menu constructors too.

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That’s some kinda strange warning, not an error! :neutral_face:

Anyways, I didn’t even know about it b/c 1 of the 1st things I do when I install Processing is turn off “Continuously check for errors” option within the PDE’s “Preferences”. :wink:

I just can’t stand that feature nagging me all the time while I type in! :face_vomiting:

7

just tried to disable it, and it still shows the message and refuses to load the sketch.

image
image1366Ă—768 117 KB

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  • Paying more attention now I’ve found out what’s wrong there.
  • It’s requesting a Float instead of a float!
  • Java will fail to auto-coerce a non-corresponding primitive value on such situation.
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9

awesome I failed to realise something so simple. Btw why do the two types exist, I understand that when declaring floats in a array or arrayList it has to be done, but when you are new it hard to find explanations behind the reason for this.

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For the ArrayList indeed. But vanilla arrays are more than OK w/ all 8 Java primitive datatypes.

B/c Java generics, the 1s inside the “diamond” <>, can’t have any of the 8 primitive datatypes!

So we use the corresponding wrapper classes instead:
Docs.Oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Number.html
Docs.Oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Float.html

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