Select Case in Java

import java.util.Scanner;
public class abejeroact34 {
public static void main (String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("\tMenu\n 1. Calculator\n 2. Conversion\n 3. Exit");
int choice = input.nextInt();
String alpha;
char alphabet;
String alphaa;
char alphabets;

switch (choice)
{
case 1:
{
System.out.println("\tCalculator Menu\n S. Sum\n D. Difference\n P. Product\n A. Average");
do {
System.out.println("Enter Choice");
alpha = input.next();
alphabet = alpha.charAt(0);
}
while ((((alphabet!='S') && (alphabet!='D') && (alphabet!='P') && (alphabet!='A'))));

switch (alphabet)
{
case 'S':
{
System.out.println("Sum");
}
break;
case 'D':
{
System.out.println("Difference");
}
break;
case 'P':
{
System.out.println("Product");
}
break;
case 'A':
{
System.out.println("Average");
}
break;
}
}
break;
case 2:
{
System.out.println("\tBinary Menu\n B. Binary\n D. Decimal\n H. Hex\n O. Octal");
do {
System.out.println("Enter Choice");
alphaa = input.next();
alphabets = alphaa.charAt(0);
}
while ((((alphabets!='B') && (alphabets!='D') && (alphabets!='H') && (alphabets!='O'))));

switch (alphabets)
{
case 'B':
{
System.out.println("Binary");
}
break;
case 'D':
{
System.out.println("Decimal");
}
break;
case 'H':
{
System.out.println("Hex");
}
break;
case 'O':
{
System.out.println("Octal");
}
break;
}
}
break;
case 3:
{
System.out.println("Thanks for using my Program");
break;
}
}
}
}