Java: How to create unicode from string "\u00C3" etc

Question

I have a file that has strings hand typed as \u00C3. I want to create a unicode character that is being represented by that unicode in java. I tried but could not find how. Help.

Edit: When I read the text file String will contain "\u00C3" not as unicode but as ASCII chars '\' 'u' '0' '0' '3'. I would like to form unicode character from that ASCII string.

Answer 1

I picked this up somewhere on the web:

String unescape(String s) {
    int i=0, len=s.length();
    char c;
    StringBuffer sb = new StringBuffer(len);
    while (i < len) {
        c = s.charAt(i++);
        if (c == '\\') {
            if (i < len) {
                c = s.charAt(i++);
                if (c == 'u') {
                    // TODO: check that 4 more chars exist and are all hex digits
                    c = (char) Integer.parseInt(s.substring(i, i+4), 16);
                    i += 4;
                } // add other cases here as desired...
            }
        } // fall through: \ escapes itself, quotes any character but u
        sb.append(c);
    }
    return sb.toString();
}

Answer 2

Dang, I was a bit slow. Here's my solution:

package ravi;

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.regex.Pattern;
public class Ravi {

    private static final Pattern UCODE_PATTERN = Pattern.compile("\\\\u[0-9a-fA-F]{4}");

    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new FileReader("ravi.txt"));
        while (true) {
            String line = br.readLine();
            if (line == null) break;
            if (!UCODE_PATTERN.matcher(line).matches()) {
                System.err.println("Bad input: " + line);
            } else {
                String hex = line.substring(2,6);
                int number = Integer.parseInt(hex, 16);
                System.out.println(hex + " -> " + ((char) number));
            }
        }
    }

}