Regex question: replace

Question

Hi,
I'm getting into java.util.regex lately. Having used Perl for regex I'm trying to get familiar with Java's regex "spirit".
Concerning replacement we can use replaceAll or replaceFirst however:
- what if I want to replace only the third or fourth element?
- what if I want to replace second to fourth element?
in PERL we use " regex_epression_here for 2..4;" for instance.
I you would have some interesting website/tutorials related to JAVA regex that would be great.
Thanks for your help.
Rgds,
SR

Answer 1

Yep,
here is a sample of replacement in Perl
$Line =~ s/\]/|/ for 2..4; #Replace 2nd 'til
4th delimiter (]) with pipe (|)
....Based on the reference I gave earlier
import java.util.regex.*;
* A rewriter does a global substitution in the strings passed to its
* 'rewrite' method. It uses the pattern supplied to its constructor,
* and is like 'String.replaceAll' except for the fact that its
* replacement strings are generated by invoking a method you write,
* rather than from another string.
* This class is supposed to be equivalent to Ruby's 'gsub' when given
* a block. This is the nicest syntax I've managed to come up with in
* Java so far. It's not too bad, and might actually be preferable if
* you want to do the same rewriting to a number of strings in the same
* method or class.
* See the example 'main' for a sample of how to use this class.
* @author Elliott Hughes
public abstract class Rewriter_1
    private Pattern pattern;
    private Matcher matcher;
     * Constructs a rewriter using the given regular expression;
     * the syntax is the same as for 'Pattern.compile'.
    public Rewriter_1(String regularExpression)
        this.pattern = Pattern.compile(regularExpression);
     * Returns the input subsequence captured by the given group
     * during the previous match operation.
    public String group(int i)
        return matcher.group(i);
     * Overridden to compute a replacement for each match. Use
     * the method 'group' to access the captured groups.
    public abstract String replacement(int index);
     * Returns the result of rewriting 'original' by invoking
     * the method 'replacement' for each match of the regular
     * expression supplied to the constructor.
    public String rewrite(CharSequence original)
        this.matcher = pattern.matcher(original);
        StringBuffer result = new StringBuffer(original.length());
        int index = 0;
        while (matcher.find())
            matcher.appendReplacement(result, replacement(++index));
        matcher.appendTail(result);
        return result.toString();
    public static void main(String[] arguments)
        String result = new Rewriter_1("\\|")
            public String replacement(int index)
                if ((index >= 3) && (index <=5))
                    return "y";
                else
                    return group(0);
        }.rewrite("| | | | | |");
        System.out.println(result);
}