Java Puzzler, double chars

A teaser which uses char and double

The following compiles and produces an output. Can you explain why? 

char ch = 'A';
ch *= 1.5;
System.out.println(ch); // prints 'a'

Here is a hint for a simpler example. 

byte b = 100;
b /= 2.5;
System.out.println(b); // prints 40

Comments

  1. Aleksandr3 January 2012 at 11:34

    Well... Duh!
    'A' is 65.
    'a' is 97

    65 * 1.5 = 97.5

    And since char is an integer...

    ReplyDelete
  2. Vladimir Dolzhenko3 January 2012 at 11:48

    @Aleksandr

    char isn't an integer - it's unsigned integer

    ReplyDelete
  3. Peter Lawrey3 January 2012 at 11:52

    Or being pedantic, char is an unsigned short. ;)

    ReplyDelete
  4. Vladimir Dolzhenko3 January 2012 at 12:49

    That's another java puzzler.

    JLS the 3rd edition:
    The Unicode standard was originally designed as a fixed-width 16-bit character encoding. It has since been changed to allow for characters whose representation requires more than 16 bits. The range of legal code points is now U+0000 to U+10FFFF, using the hexadecimal U+n notation.

    So, it is not a 32-bit integer, in the same time it definitely more than short.

    ReplyDelete
  5. Peter Lawrey3 January 2012 at 13:12

    @Vladimir The String and Character classes now support "code points" which assume a String is UTF-16 encoded for characters. http://en.wikipedia.org/wiki/UTF-16

    In the case of Character there are pairs of methods.

    public static boolean isLowerCase(char ch)

    public static boolean isLowerCase(int codePoint)

    http://docs.oracle.com/javase/7/docs/api/java/lang/Character.html


    Character.MAX_VALUE is still 65535, and char is still 16-bit, but code points use int values though as you point out, not the full range of 32-bit values. ;)

    ReplyDelete

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