Recipe 3.6 Converting Between Unicode Characters and Strings


Problem

You want to convert between Unicode characters and Strings.

Solution

Since both Java char values and Unicode characters are 16 bits in width, a char can hold any Unicode character. The charAt( ) method of String returns a Unicode character. The StringBuilder append( ) method has a form that accepts a char. Since char is an integer type, you can even do arithmetic on chars, though this is not necessary as frequently as in, say, C. Nor is it often recommended, since the Character class provides the methods for which these operations were normally used in languages such as C. Here is a program that uses arithmetic on chars to control a loop, and also appends the characters into a StringBuilder (see Recipe 3.3):

/**  * Conversion between Unicode characters and Strings  */ public class UnicodeChars {     public static void main(String[] argv) {         StringBuffer b = new StringBuffer( );         for (char c = 'a'; c<'d'; c++) {             b.append(c);         }         b.append('\u00a5');    // Japanese Yen symbol         b.append('\u01FC');    // Roman AE with acute accent         b.append('\u0391');    // GREEK Capital Alpha         b.append('\u03A9');    // GREEK Capital Omega         for (int i=0; i<b.length( ); i++) {             System.out.println("Character #" + i + " is " + b.charAt(i));         }         System.out.println("Accumulated characters are " + b);     } }

When you run it, the expected results are printed for the ASCII characters. On my Unix system, the default fonts don't include all the additional characters, so they are either omitted or mapped to irregular characters (Recipe 13.3 shows how to draw text in other fonts):

C:\javasrc\strings>java  UnicodeChars Character #0 is a Character #1 is b Character #2 is c Character #3 is % Character #4 is | Character #5 is Character #6 is ) Accumulated characters are abc%|)

My Windows system doesn't have most of those characters either, but at least it prints the ones it knows are lacking as question marks (Windows system fonts are more homogenous than those of the various Unix systems, so it is easier to know what won't work). On the other hand, it tries to print the Yen sign as a Spanish capital Enye (N with a ~ over it). Amusingly, if I capture the console log under Windows into a file and display it under Unix, the Yen symbol now appears:

Character #0 is a Character #1 is b Character #2 is c Character #3 is ¥ Character #4 is ? Character #5 is ? Character #6 is ? Accumulated characters are abc¥???

See Also

The Unicode program in this book's online source displays any 256-character section of the Unicode character set. Documentation listing every character in the Unicode character set can be downloaded from the Unicode Consortium at http://www.unicode.org.



Java Cookbook
Java Cookbook, Second Edition
ISBN: 0596007019
EAN: 2147483647
Year: 2003
Pages: 409
Authors: Ian F Darwin

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