Using Dr.Java, why does ♂ equal something different in the interaction pane than when programmed

Question

When using the code below

int count = 0;
while(count != '♂'){
    count++;
}
System.out.print(count);

in the interactions pane in dr java, it equals the correct unicode number (9794), but when done in the programming pane , it returns 63, using the exact same code.

Why is that ?

This is getting complicated,

when using this code in the interactions pane

import java.util.Scanner;
Scanner scan = new Scanner(System.in);
int count = 0;
String letter = scan.next();

input is ♂

while(count != letter.charAt(0)){
    count++;
}

it returns 66, and same in the programming pane,

Sounds like a bug in DrJava's programming pane, not handling Unicode correctly. — T.J. Crowder, Dec 11 '14 at 07:48

score 1 · Accepted Answer · answered Dec 11 '14 at 07:49

1

Character encoding depends on the system. Depending on your box, it may print the 16 bits of the UTF-16 encoding (which is 9794), the high 8 bits (which would be 38) or, as in your case, the low 8 bits (which is 66).

9794 / 256 = 38
9794 % 256 = 66

answered Dec 11 '14 at 07:49

llogiq

13,815
8
40
72

I dont quite understand what you mean by the low 8 bits and the high 8 bits – David Huntington Dec 11 '14 at 08:53
A java char is 16 bits, which can be split in two 8-bit-parts. You can re-combine the parts by multiplying the "high" part by 256 and adding the low part. In your case 36 * 256 + 66 = 9794. – llogiq Dec 11 '14 at 09:10
just realised a mistake in the question, when programmed it outputs 64, not 66, so would the low 8 be 64 ? – David Huntington Dec 11 '14 at 09:28
woops, i meant 63, not 64. – David Huntington Dec 11 '14 at 09:42
That depends mostly on your tool's encoding, then. – llogiq Dec 11 '14 at 11:51
@DavidHuntington if you made mistake in your post, why did not you edit it? – Kick Buttowski Dec 11 '14 at 17:52

paxdiablo · Answer 2 · 2014-12-11T09:04:19.537

0

It appears to be a problem with the tools you're using, which is probably a good reason to stop using them :-)

The male symbol, U+2642 (see here) has 0x42 as the final octet (from 0x26 0x42) which, in decimal, is 66 (4 x 16 + 2).

edited Dec 11 '14 at 09:04

answered Dec 11 '14 at 07:55

paxdiablo

854,327
234
1,573
1,953

I understand that U+ is unicode, but the OX i dont understand where that comes from ? could you explain ? – David Huntington Dec 11 '14 at 08:54
@David, `0xNN` is a way of specifying a hexadecimal number, especially by old C die-hards like myself. What I'm saying is that the tool you're using does not seem to fully subscribe to the Unicode way of thinking, in that it's only using the lower eight bits (`0x42` or decimal `66`) of the value for comparison. – paxdiablo Dec 11 '14 at 09:06

score 0 · Answer 3 · answered Dec 11 '14 at 10:03

when done in the programming pane , it returns 63, using the exact same code.

Character 63 is the question mark ?. This is used as a placeholder for when a character you have used cannot be written in the encoding you are writing to.

I'm assuming by “programming pane” you mean the main source code editor. This content is saved to a file before being compiled, so it has to be saved using a particular encoding. Unfortunately it looks like DrJava doesn't give you the option to save files as anything other than the system default code page, probably in your case Windows code page 1252. This encoding does not include the character ♂, so it gets replaced by ?.

So it looks like with your current workflow you will sadly have to stick to ASCII-only source, and consequently say:

while (count != '\u2642') { ...

Using Dr.Java, why does ♂ equal something different in the interaction pane than when programmed

when using this code in the interactions pane

3 Answers3

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