Arreglos en java

//CalculadoraMetodo.java

import javax.swing.*;

public class CalculadoraMetodo{

        public static void main (String[]args){

                String menu = "" , op;

                menu += "1-.Suma\n";

                menu += "2-.Resta\n";

                menu += "3-.Salir\n";

                menu += "Digita una opcion\n";

                int opc=0;

                while (opc != 3){

                op = JOptionPane.showInputDialog(null,menu,"Calculadora",3);

                opc = Integer.parseInt(op);

                switch(opc){

                        case 1:

                        suma();

                        break;

                        case 2:

                        resta();

                        break;

                }

                }

        }

        public static void suma(){

                String a = JOptionPane.showInputDialog(null,"Ingrese valor de A","Suma",3);

                String b = JOptionPane.showInputDialog(null,"Ingrese valor de B","Suma",3);

                int aa,bb,c;

                aa = Integer.parseInt(a);

                bb = Integer.parseInt(b);

                c = aa + bb;

                JOptionPane.showMessageDialog(null,"Suma = "+c ,"Suma",1);

        }

        public static void resta(){

                String a = JOptionPane.showInputDialog(null,"Ingrese valor de A","Resta",3);

                String b = JOptionPane.showInputDialog(null,"Ingrese valor de B","Resta",3);

                int aa,bb,c;

                aa = Integer.parseInt(a);

                bb = Integer.parseInt(b);

                c = aa - bb;

...