Touring Language APIs - Beginning Java 7 - page 324

Character
Character isthelargestoftheprimitivetypewrapperclasses,containingmanycon-
stants,aconstructor,manymethods,andatrioofnestedclasses( Subset , UnicodeB-
lock , and UnicodeScript ).
Note Character 's complexity derives from Java's support for Unicode ( y ) . For
brevity,Iignoremuchof Character 'sUnicode-relatedcomplexity,whichisbeyond
the scope of this chapter.
Character declares a single Character(char value) constructor, which
youusetoinitializea Character objectto value .Thisconstructoriscomplemented
by char charValue() , which returns the wrapped character value.
When you start writing applications, you might codify expressions such as ch >=
'0' && ch <= '9' (test ch toseeifitcontainsadigit)and ch >= 'A' && ch
<= 'Z' (test ch to see if it contains an uppercase letter). You should avoid doing so
for three reasons:
• Itistooeasytointroduceabugintotheexpression.Forexample, ch > '0'
&& ch <= '9' introducesasubtlebugthatdoesnotinclude '0' inthecom-
parison.
• The expressions are not very descriptive of what they are testing.
• TheexpressionsarebiasedtowardLatindigits(0-9)andletters(A-Zanda-z).
Theydonottakeintoaccountdigitsandlettersthatarevalidinotherlanguages.
Forexample, '\u0beb' isacharacterliteralrepresentingoneofthedigitsin
the Tamil language.
Character declaresseveralcomparisonandconversionclassmethodsthataddress
these concerns. These methods include the following:
• static boolean isDigit(char ch) returnstruewhen ch containsa
digit (typically 0 through 9, but also digits in other alphabets).
• static boolean isLetter(char ch) returnstruewhen ch contains
a letter (typically A-Z or a-z, but also letters in other alphabets).
• static boolean isLetterOrDigit(char ch) returnstruewhen c h
containsaletterordigit(typicallyA-Z,a-z,or0-9;butalsolettersordigitsin
other alphabets).
• static boolean isLowerCase(char ch) returnstruewhen ch con-
tains a lowercase letter.