Java字符串 正则表达式详解

String len="^[A-Z].*[\\.]$";
System.out.println("Taaa.".matches(len));//true
System.out.println("taaa.".matches(len));//false
System.out.println("Taaa".matches(len));//false

private Pattern(String p, int f) {
    pattern = p;
    flags = f;

    // to use UNICODE_CASE if UNICODE_CHARACTER_CLASS present
    if ((flags & UNICODE_CHARACTER_CLASS) != 0)
        flags |= UNICODE_CASE;

    // Reset group index count
    capturingGroupCount = 1;
    localCount = 0;

    if (!pattern.isEmpty()) {
        try {
            compile();
        } catch (StackOverflowError soe) {
            throw error("Stack overflow during pattern compilation");
        }
    } else {
        root = new Start(lastAccept);
        matchRoot = lastAccept;
    }
}

public static Pattern compile(String regex) {
    return new Pattern(regex, 0);
}

public Matcher matcher(CharSequence input) {
    if (!compiled) {
        synchronized(this) {
            if (!compiled)
                compile();
        }
    }
    Matcher m = new Matcher(this, input);
    return m;
}

public static boolean matches(String regex, CharSequence input) {
    Pattern p = Pattern.compile(regex);
    Matcher m = p.matcher(input);
    return m.matches();
}

Pattern len = Pattern.compile("^[A-Z].*[\\.]$");
Matcher matcher = len.matcher("Taaa.");
boolean matches = matcher.matches();
System.out.println(matches);

System.out.println(Pattern.matches("^[A-Z].*[\\.]$","Taaa."));

public String[] split(CharSequence input, int limit) {
    int index = 0;
    boolean matchLimited = limit > 0;
    ArrayList<String> matchList = new ArrayList<>();
    Matcher m = matcher(input);

    // Add segments before each match found
    while(m.find()) {
        if (!matchLimited || matchList.size() < limit - 1) {
            if (index == 0 && index == m.start() && m.start() == m.end()) {
                // no empty leading substring included for zero-width match
                // at the beginning of the input char sequence.
                continue;
            }
            String match = input.subSequence(index, m.start()).toString();
            matchList.add(match);
            index = m.end();
        } else if (matchList.size() == limit - 1) { // last one
            String match = input.subSequence(index,
                                             input.length()).toString();
            matchList.add(match);
            index = m.end();
        }
    }

    // If no match was found, return this
    if (index == 0)
        return new String[] {input.toString()};

    // Add remaining segment
    if (!matchLimited || matchList.size() < limit)
        matchList.add(input.subSequence(index, input.length()).toString());

    // Construct result
    int resultSize = matchList.size();
    if (limit == 0)
        while (resultSize > 0 && matchList.get(resultSize-1).equals(""))
            resultSize--;
    String[] result = new String[resultSize];
    return matchList.subList(0, resultSize).toArray(result);
}