Substitute " " for   with the AwkTools regular expression classes, Some trouble?

[Surfbird Fang <su...@hotmail.com>]

When I want to subsitute " " for   in a html file with AWK, I write the following code.But some trouble arise.

Then console report the error message :

java.lang.ArrayIndexOutOfBoundsException
        at org.apache.oro.text.awk.AwkMatcher._search(AwkMatcher.java:717)
        at org.apache.oro.text.awk.AwkMatcher.contains(AwkMatcher.java:622)
        at test.Test.removeBlankspaceEntity(Test.java:58)
        at test.Test.<init>(Test.java:27)
        at test.Test.main(Test.java:82)


the code following 
============================


        String regex = "(&nbsp;)";
        String sentence=null;
        AwkMatcher matcher;
        AwkCompiler compiler;
        Pattern pattern = null, blankspace = null;
        AwkStreamInput input;
        MatchResult result;
        Reader file = null;

        // Create AwkCompiler and AwkMatcher instances.
        compiler = new AwkCompiler();
        matcher  = new AwkMatcher();


        pattern = compiler.compile(regex, AwkCompiler.CASE_INSENSITIVE_MASK);
        blankspace = compiler.compile("(&nbsp;)");
        file = new FileReader(src);
        input = new AwkStreamInput(file);
        while(matcher.contains(input, pattern)) {
            result = matcher.getMatch();
            sentence = Util.substitute(matcher, blankspace,
                                         new StringSubstitution(" "),
                                         result.toString(), Util.SUBSTITUTE_ALL);

        }


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What happen? Do I write regular expression error? 

Thanks in advance
Surfbird