Plssss someone help me in JAVA?

I have the code here name the file as ifmdas.java:

(the code is)

```
import java.io.*;
public class ifmdas{
public static void main(String[] args) throws IOException{
BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
String option, firstnum, secondnum;
int num1, num2, prod, quo, sum, diff, choice;
System.out.print("Choose An Operation");
System.out.print("\nPress1 for Multiplication");
System.out.print("\nPress2 for Division");
System.out.print("\nPress3 for Addition");
System.out.print("\nPress4 for Subtraction");
System.out.print("\n\nOperation: ");
option=stdin.readLine();
choice=Integer.parseInt(option);
if(choice==1){
System.out.print("\nEnter the first number");
firstnum=stdin.readLine();
System.out.print("\nEnter the second number");
secondnum=stdin.readLine();
num1=Integer.parseInt(firstnum);
num2=Integer.parseInt(secondnum);
prod=num1*num2;
System.out.print("\nThe product is: "+prod);
}else if(choice==2){
System.out.print("\nEnter the first number");
firstnum=stdin.readLine();
System.out.print("\nEnter the second number");
secondnum=stdin.readLine();
num1=Integer.parseInt(firstnum);
num2=Integer.parseInt(secondnum);
if(num2==0){
System.out.print("cannot perform the operation");
}else{
quo=num1/num2;
System.out.print("\nThe quotient is: "+quo);
}
}
else if(choice==3){
System.out.print("\nEnter the first number");
firstnum=stdin.readLine();
System.out.print("\nEnter the second number");
secondnum=stdin.readLine();
num1=Integer.parseInt(firstnum);
num2=Integer.parseInt(secondnum);
sum=num1+num2;
System.out.print("\nThe sum is: "+sum);
}
else if(choice==4){
System.out.print("\nEnter the first number");
firstnum=stdin.readLine();
System.out.print("\nEnter the second number");
secondnum=stdin.readLine();
num1=Integer.parseInt(firstnum);
num2=Integer.parseInt(secondnum);
diff=num1-num2;
System.out.print("\nThe diference is: "+diff);
}
}
}
```

i wanna have now the option that uses only big and small characters ( M,D,A,S) and (m,d,a,s) i think this one will use bool character but I didn't know how to do the bool

so please someone recode this java file plsss help