字符串

1  字符串补位

   String f = "%05d";
   System.out.println(String.format(f, 100)); //在100的左边补0 ， 总共有5位
   String str1=String.format("%-7s", "100").replaceAll(" ", "0"); //在右边补0,可以将0换成其他的字符
   System.out.println(str1);
   String str2=String.format("%7s", "100").replaceAll(" ", "0"); //在左边补0,可以将0换成其他的字符
   System.out.println(str2);

　　

2 字符串replace

 String []  arr =  new String[] {"abc","def","ert"};
 System.out.println(Arrays.toString(arr));  //[abc, def, ert]
 System.out.println(Arrays.toString(arr).replaceAll("\\[|\\]", "").replaceAll(",\\s", ",")); //abc,def,ert

 

3 找出字符串中所有满足格式的子字符串

    /**
     *   打印结果#{userAge} ，#{userName}
     * @param args
     */
    public static void main(String[] args) {
        String sql = "update user set userAge = #{userAge}  where userName = #{userName} ";
        Pattern pattern = Pattern.compile("#\\{.*?\\}");
        Matcher matcher = pattern.matcher(sql);
        while (matcher.find()) {
            String e = matcher.group(0);
            System.out.println(e);
        }
    }

 

4 字符串格式化