如何使用java String.replaceAll（字符串正则表达式，字符串替换）来获取我想要的？

Question

Codes:

  String etr = "fdsfsdaf\nTKT:1101234567890FSDFD";

the format is like ".+\\nTKT:\\d{13}.+".

how to get first 3 numberic after "\\nTKT:" using String.replaceAll to implement? In this example, I want to get is "110". Exclude Matcher,Pattern and Other String method like indexOf(). Because I found the Regex include "?:","?<",but I have tried but failed,something like":

      replaceAll(".+\nTKT:(?=[\\d{3}])\\d{10}.+","");

Thanks in advance.I just know some basic use for Regex.

Answer 1

或者，您也可以replaceAll(".+\\nTKT:(\\\\d{3})\\\\d{10}.+", "$1");

Answer 2

Instead of replacing,you should match it

Matcher m=Pattern.compile(".+\nTKT:(\\d{3})\\d{10}.+").matcher(input);
if(m.find())
{
    m.group(1);
}