练习1

String str= "我我我   要要要   要 学学学   编编编   编编 编程程程 程程。";        String regex=" +";        str=str.replaceAll(regex, "");        regex ="(.)\\1+";        str=str.replaceAll(regex, "$1");        System.out.println(str);

练习2

//将下列ip排序        String str= "192.68.1.254 102.49.23.013 10.10.10.10 2.2.2.2 8.109.90.30";        //在前面加俩零        str=str.replaceAll("(\\d+)","00$1" );        //取后三位        str=str.replaceAll("0*(\\d{3})","$1" );        //切割                String[] ips =  str.split(" +");        Arrays.sort(ips);        for(String ip :ips)        {            ip=ip.replaceAll("0*(\\d+)", "$1");                        System.out.println(ip);                    }