1, Java - rextester

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//'main' method must be in a class 'Rextester'.
//openjdk version '11.0.5'

import java.util.*;
import java.lang.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

class Rextester
{  
    public static void main(String args[])
    {
        String string = "Added new temp file C:\\Users\\SBT-EP~1\\AppData\\Local\\Temp\\xmlmiddle6835249412414154912.tmp\n"
             + "Added new temp file C:\\Users\\SBT-EP~1\\AppData\\Local\\Temp\\xmlmiddle5440891082300867141.tmp\n"
             + "Added new temp file C:\\Users\\SBT-EP~1\\AppData\\Local\\Temp\\xmlmiddle1785426108627598179.tmp\n";
        
        Pattern pattern = Pattern.compile("xmlmiddle(\\d{19})");
        Matcher matcher = pattern.matcher(string);
        if (matcher.find()) {
            System.out.println("match: " + matcher.group(1));
        }
        
        pattern = Pattern.compile("xmlmiddle\\d{19}(?s).*?xmlmiddle(\\d{19})");
        matcher = pattern.matcher(string);
        if (matcher.find()) {
            System.out.println("match: " + matcher.group(1));
        }
        
        pattern = Pattern.compile("xmlmiddle\\d{19}(?s).*?xmlmiddle\\d{19}.*?xmlmiddle(\\d{19})");
        matcher = pattern.matcher(string);
        if (matcher.find()) {
            System.out.println("match: " + matcher.group(1));
        }
    }
}

[ + ] Show input
Compilation time: 0.72 sec, absolute running time: 0.24 sec, cpu time: 0.18 sec, memory peak: 38 Mb, absolute service time: 1,08 sec