Create a timer button to automatically switch off or end task

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Java

Eclipse

I want to create a stanby button where when user clicks the standby button, it means user is leaving the device still on but when it is left for 5 minutes, the device will automatically turns off.

This is what I have come up with so far but where do I implement the timer function?

What I have tried:

import java.util.Scanner;

public class StandbyMode {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("Standby Mode");
        System.out.println("Press 1 for Standby mode");
        System.out.println("Press 2 to disable");
        int selectedOption = scanner.nextInt();
        if(selectedOption == 1){
            System.out.println("Standby mode is enabled");

          }else {
            System.out.println("Standby Mode disabled");

        }

    scanner.close();
  }

}