/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String a = "Pet_you.txt";
        String b = "pet_te_you.txt";
        System.out.println(extract(a));
        System.out.println(extract(b));
        System.out.println(anotherExtract(a));
        System.out.println(anotherExtract(b));
	}
 
	    static String extract(String s) {
        StringBuilder sb = new StringBuilder();
        for (int i = s.lastIndexOf(".") - 1; i > 0; i--) {
            if (Character.isAlphabetic(s.charAt(i))) {
                sb.append(s.charAt(i));
            } else {
                break;
            }
        }
        return sb.reverse().toString();
    }
 
    static String anotherExtract(String s) {
        //s = s.substring(s.lastIndexOf("_") + 1);
        return s = s.substring(s.lastIndexOf("_") + 1).substring(0, s.substring(s.lastIndexOf("_") + 1).lastIndexOf("."));
    }
}

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