kalkulator.java

package kalkulator;

public class Kalkulator {

    private static Kalkulator instance;

    public static final int KALKULATOR_PENAMBAHAN = 0;
    public static final int KALKULATOR_PERKALIAN = 1;
    public static final int KALKULATOR_PEMBAGIAN = 2;
    public static final int KALKULATOR_PENGURANGAN = 3;

    private int Operator;

    private Kalkulator() {
    }

    public static Kalkulator newInstance() {
        if (instance == null) {
            instance = new Kalkulator();
        }
        return instance;
    }

    public Kalkulator setOperator(int Operator) {
        instance.Operator = Operator;
        return instance;
    }

    public double hitung(double nilaiA, double nilaiB) {
        switch (instance.Operator) {
            case KALKULATOR_PEMBAGIAN:
                return nilaiA / nilaiB;
            case KALKULATOR_PENAMBAHAN:
                return nilaiA + nilaiB;
            case KALKULATOR_PENGURANGAN:
                return nilaiA - nilaiB;
            case KALKULATOR_PERKALIAN:
                return nilaiA * nilaiB;
            default:
                return 0;

        }
    }
}