so i have this method it's half written and i'm having a terrible time understanding how to complete the operands can someone help me complete the rest of the switch cases for +, - , * , / in java

rivate static double calculateSpacedPostfix(String postfixSpaced) {

Scanner scan = new Scanner(postfixSpaced);

StackInterface operands = new LinkedStack<>();

while(scan.hasNext()) {

String token = scan.next();

switch(token) {

case "+":

double result = 0;

while(operands.peek() != null){

result += operands.pop();

}

break;

case "(":

break;

case ")":

break;

default:

double value = Double.parseDouble(token);

operands.push(value); // Put each operand on the stack

}

}

scan.close();

return 0;

}

}