The addDecimal method adds a decimal point to the operand. Then it returns the period character. This method needs to be handled carefully because only one decimal is allowed in an operand. Use the String method contains to help you here.

package calcrpn; 1 2 3 import java.util.Stack; 4 5 public class CalcBrain implements CalcRPNOperations { 7 Stack results; String operand; 8 9 10 2 12 13 public CalcBrain() { results = new Stack(); operand }