calculator zadaca

prvo pravime interfejs za olesnuvanje na metodite / kalkulaciite
package AV4;

public interface Strategy {

    double calculate(double num1, double num2);
}
 potoa pravime nova klasa koja go implementira toj interfejs
package AV4;

public class Addition implements Strategy{
    @Override
    public double calculate(double num1, double num2) {
        return num1+num2;
    }
}
i na kraj vo originalnata calculator klasa
public class Calculator {
    private double rezultat;
    private Strategy strategy;

    public Calculator(double rezultat) {
        this.rezultat = 0.0;
    }

    public String execute(char operation, double value) {
        if (operation == '+') {
            strategy= new Addition();