How does Java compare an inputted string with the name of a variable?

Question

I need to use the input which is a string to "identify" an already declared variable. If "tripple" is inputted than java need to somehow get that the variable tripple is meaned by the input "tripple". I am doing that because I need to add its value(3, because int tripple = 3) to another variable(Integer).

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner();
    int double = 2
    int tripple = 3
    int startpos = 0 

    String inputting = scan.next();  //input is for example ---> tripple 
    startpos = startpos + (???)
    
    //After inputting "tripple", startpos should be 3
    
    System.out.println(startpos); //---> 3 
  }
}

I tried to get an input and adress the variable that has the same name as the input which is a string. I didn't know what to do, so I asked my teacher and she also do not know what to do so I am asking it to you.