使用intAt作为Switch

Question

我很难理解为什么intAt无法在此计划中发挥作用。该计划的目标是简单地转换特定行星的权重。

package weightonotherplanets;
import java.util.Scanner; 

public class WeightonOtherPlanets 
{
    public static void main(String args[]){     
        System.out.println("What is your weight on the Earth?");

        Scanner weightInput = new Scanner(System.in); // Enter your weight
        int weight = weightInput.nextInt(); 

        System.out.println("1. Voltar\n2. Krypton\n3. Fertos\n4. Servontos\n"); // Choice of planets
        System.out.println("    Selection?");

        Scanner selectionChoice = new Scanner(System.in);
        int selection = selectionChoice.nextInt();
        int select = selection.intAt(0); // This is the problem in the code

        switch (select)
        {
            case '1': 
                System.out.println("Your weight on Voltor would be " + weight * 0.091);
                break;
            case '2':
                System.out.println("Your weight on Krypton would be " + weight * 0.720);
                break;
            case '3':
                System.out.println("Your weight on Fertos would be " + weight * 0.865);
                break;
            case '4':
                System.out.println("Your weight on Servontos would be " + weight * 4.612);
                break;
            default:
                System.out.println("Please make a selection.");

        }
    }
}