Hi J-gurus! Wondering about how I am supposed to understand the following type of question in one book preparing for JSCP certificate. The question was... What is the numerical range of a char? This option was given as one choice -(2^15) to (2^15)-1 My opinion is that I should count above statements as bitwise operation as follows: 0000010 2 ^ 0001111 15 ----------------- 0001101 13 But not as Math.pow(2,15) Am I right? janne
Joined: Aug 25, 2003
Hi Janne, char is really an unsigned int data type. It can't be negative. char is defined by Unicode notation occupying 2 bytes, which gives you 2 to the power of 16 combinations or valid char values. The values start from 0 and end at (2 ^ 16) - 1. ^ here is just a substitute for power, not an XOR operator. JLS:
4.2.1 Integral Types and Values The values of the integral types are integers in the following ranges: � For byte, from �128 to 127, inclusive � For short, from �32768 to 32767, inclusive � For int, from �2147483648 to 2147483647, inclusive � For long, from �9223372036854775808 to 9223372036854775807, inclusive � For char, from '\u0000' to '\uffff' inclusive, that is, from 0 to 65535
And this is also from JLS:
� For type char, the default value is the null character, that is, '\u0000'.
And another useful quote from JLS:
3.10.4 Character Literals A character literal is expressed as a character or an escape sequence, enclosed in ASCII single quotes. (The single-quote, or apostrophe, character is \u0027.) A character literal is always of type char. CharacterLiteral: ' SingleCharacter ' ' EscapeSequence ' SingleCharacter: InputCharacter but not ' or \ The escape sequences are described in �3.10.6. As specified in �3.4, the characters CR and LF are never an InputCharacter; they are recognized as constituting a LineTerminator. It is a compile-time error for the character following the SingleCharacter or EscapeSequence to be other than a '. It is a compile-time error for a line terminator to appear after the opening ' and before the closing '. The following are examples of char literals: 'a' '%' '\t' '\\' '\'' '\u03a9' '\uFFFF' '\177' 'W' '�' Because Unicode escapes are processed very early, it is not correct to write '\u000a' for a character literal whose value is linefeed (LF); the Unicode escape \u000a is transformed into an actual linefeed in translation step 1 (�3.3) and the linefeed becomes a LineTerminator in step 2 (�3.4), and so the character literal is not valid in step 3. Instead, one should use the escape sequence '\n' (�3.10.6). Similarly, it is not correct to write '\u000d' for a character literal whose value is carriage return (CR). Instead, use '\r'. In C and C++, a character literal may contain representations of more than one character, but the value of such a character literal is implementation-defined. In the Java programming language, a character literal always represents exactly one character.
[ November 12, 2003: Message edited by: Vad Fogel ]