Taschenrechner mit OOP

package calculator;
import java.util.EmptyStackException;
import java.util.Scanner;

public class Calculator {
    static Scanner in = new Scanner(System.in);

    private static Memory calcMemory = new Memory();

    private static Verwalter calcVerwalter = new Verwalter();

    private void saveInStack(double userInput, Memory calcMemory) {
        calcMemory.push(userInput);
    }

    public static void main(String[] args) throws EmptyStackException {
        Calculator calc = new Calculator();

        registerAllOperations(calcVerwalter);

        // Eingabe von Konsole an Memory
        while (true) {
            if (calcMemory.isEmpty()) {
                System.out.println("Der Speicher ist leer. Bitte geben Sie eine Zahl ein.");
            }

            System.out.println("Eingabe: ");

            String userInput = in.next();
            executeInput(userInput, calc, calcVerwalter, calcMemory);

            System.out.println("Stack [" + calcMemory.toString() + "]");
            System.out.println("");
        }
    }

    static Memory executeInput(String userInput, Calculator calc, Verwalter verwalter, Memory calcMemory) {

        //Cache, um bei EmptyStackException die erste Eingabe wiederherzustellen.

        Double[] dump = calcMemory.dumpStack();

        try {
            Double numberInput = Double.parseDouble(userInput);
            calc.saveInStack(numberInput, calcMemory);
        } catch (NumberFormatException e) {
            try {
                String symbolInput = userInput;
                verwalter.executeOperation(symbolInput, calcMemory);
            } catch (EmptyStackException a) {
                //Exception, wenn Rechenoperation weitere Werte benötigt
                System.out
                        .println("Die letzte Rechenoperation benötigt mehr Werte. Bitte geben Sie eine weitere Zahl ein.");
                calcMemory.restoreStack(dump);

            }
        }
        return calcMemory;
    }

    static void registerAllOperations(Verwalter verwalter) {
        //Registrieren aller möglichen Rechenoperationen
        verwalter.register(new Addition());
        verwalter.register(new Division());
        verwalter.register(new Multiplication());
        verwalter.register(new Potency());
        verwalter.register(new Square());
        verwalter.register(new SquareRoot());
        verwalter.register(new Subtraction());
        verwalter.register(new TopAverage());
        verwalter.register(new TopSum());
    }

}

package calculator;

import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.NumberFormat;
import java.util.*;

public class Memory {

    private Stack<Double> calcMemory = new Stack<Double>();

    void push(double numIn) {
        calcMemory.push(numIn);
    }

    double pop() {
        double numOut = calcMemory.pop();
        return numOut;
    }

    @Override
    public String toString() {
        String output = "";
        for (int i = 0; i < calcMemory.size(); i++) {
            output += formatNumber(calcMemory.elementAt(i));
            if (i != calcMemory.size() - 1) {
                output += " | ";
            }
        }
        return output;
    }

    boolean isEmpty() {
        if (!calcMemory.isEmpty()) {

            return false;
        }
        return true;
    }

    int size() {
        return calcMemory.size();
    }
//dump to reset memory in case of invalid user input
    Double[] dumpStack() {
        Double[] content = calcMemory.toArray(new Double[0]);

        return content;
    }

    void restoreStack(Double[] dump) {
        calcMemory.clear();
        for (Double d : dump) {
            calcMemory.push(d);
        }

    }

    // Nachkommastellen
    private static String formatNumber(double number) {
        /* always use German decimal formatter symbols (, and .) */
        DecimalFormatSymbols decimalFormatSymbols = DecimalFormatSymbols.getInstance(Locale.GERMANY);
        NumberFormat formatter = new DecimalFormat("#0.####", decimalFormatSymbols);
        return formatter.format(number);
    }

}

package calculator;

import java.util.ArrayList;
import java.util.List;

public class Verwalter {

    private List<Operation> registered = new ArrayList<Operation>();

    void register(Operation o) {
        registered.add(o);
    }

    boolean isRegistered(Operation o) {
        return registered.contains(o);
    }

    void executeOperation(String symbolToSearch, Memory stack) {
        for (int i = 0; i < registered.size(); i++) {
            Operation search = registered.get(i);

            if (search.isMatchingSymbol(symbolToSearch)) {
                search.calculate(stack);
            }
        }
    }


}

package calculator;

public interface Operation {

    public void calculate(Memory stack);
   
    public boolean isMatchingSymbol(String userInputSymbol);
   
}

package calculator;

public class Addition implements Operation {

    public void calculate(Memory stack) {
        double sub1 = stack.pop();
        double sub2 = stack.pop();       
       
        stack.push(sub1 + sub2);
      
    }

    @Override
    public boolean isMatchingSymbol(String userInputSymbol) {
        return userInputSymbol.equals("+");
    }

}