判断一个字符串是否为IP地址

    private boolean isIpAddress(String value) {
       
        int start = 0;
        int end = value.indexOf('.');
        int numBlocks = 0;
       
        while (start < value.length()) {
           
            if (end == -1) {
                end = value.length();
            }

            try {
                int block = Integer.parseInt(value.substring(start, end));
                if ((block > 255) || (block < 0)) {
                    return false;
                }
            } catch (NumberFormatException e) {
                return false;
            }
           
            numBlocks++;
           
            start = end + 1;
            end = value.indexOf('.', start);
        }
       
        return numBlocks == 4;
    }