David Hovemeyer's and Bill Pugh's "findbugs" program have found some bugs in
Pattern.java. David writes:

M Dm: java.util.regex.Pattern.normalizeCharClass(StringBuffer,int) invokes dubious new String(String) constructor; just use
 the argument At Pattern.java:[line 1211]

        if (eq != null) {
            result = new String("(?:"+charClass.toString()+
                                eq.toString()+")");
        } else {
            result = charClass.toString();
        }

Just slow and embarrassing. Should be:


        if (eq != null) {
            result = "(?:"+charClass.toString()+
                                eq.toString()+")";
        } else {
            result = charClass.toString();
        }

----

M Dm: java.util.regex.Pattern.produceEquivalentAlternation(String) invokes dubious new String(String) constructor; just use
 the argument At Pattern.java:[line 1230]

    private String produceEquivalentAlternation(String source) {
        int len = countChars(source, 0, 1);
        if (source.length() == len)
            // source has one character.
            return new String(source); // should be return source;

ditto.