This was fixed using the split method in the string class as so
public static void stackRPN(){
Stack myStack = new Stack();
Scanner sc = new Scanner(System.in);
System.out.print("Enter an equation: ");
System.out.println();
String eq = sc.nextLine();
//This Bit splits up the string where it meets a space
String[] eqS = eq.split(" ");
int len = eqS.length;
for (int i = 0; i < len; i++){
String car1 = eqS[i];
if ("+".equals(car1) || "-".equals(car1) || "/".equals(car1) || /*"car1"*/"x".equals(car1)){
String a = myStack.pop();
String b = myStack.pop();
//This handlws all the digits
double bI = Double.parseDouble(b);
double aI = Double.parseDouble(a);
double finalNo = 0;
switch (car1) {
case "+": finalNo = bI + aI;
break;
case "-": finalNo = bI - aI;
break;
case "/": finalNo = bI / aI;
break;
case "x": finalNo = bI * aI;
break;
}
myStack.push(finalNo+"");
String finEq = b+car1+a;
System.out.println(finEq + " = " +finalNo);
} else {
myStack.push(car1);
}
}
mainMenu();
}