Currently there are be 4 combinations

• Add hours.
• Add days.
• Subtract hours.
• Subtract days.

private String modifyDate(Character symbol, LocalDateTime date, Long digits, String period) {
        switch (symbol) {
            case ' ':
                if (period.contains("days")) {
                    return date.plusDays(digits).toString();
                } else {
                    return date.plusHours(digits).toString();
                }
            case '-':
                if (period.contains("days")) {
                    return date.minusDays(digits).toString();
                } else {
                    return date.minusHours(digits).toString();
                }
            default:
                System.out.println("Not defined operation");
        }

        return "";
    }

If a new period is added (let's say years), it will be necessary to add a new if statement in each case:

if (period.contains("years")) {
    return date.plusYears(digits).toString();
} else if (period.contains("days")) {
    return date.plusDays(digits).toString();
} else {
    return date.plusHours(digits).toString();
}

Also if a new unexpected case is added (a combination, especial cases), then it will be necessary to repeat the logic to validate the periods.

Do you have a recommendation to improve the solution? Pattern recommendation, functional interfaces implementation, any recommendation is welcome.

Thanks in advance!

CodePudding user response：

The general recommendation by Martin Fowler is to Replace Conditional with Polymorphism.

https://www.refactoring.com/catalog/replaceConditionalWithPolymorphism.html

In terms of design patterns, this would often be the Strategy Pattern Replace Conditional Logic with Strategy.

https://www.industriallogic.com/xp/refactoring/conditionalWithStrategy.html

If you have a small, finite set of conditions, I recommend using an enum to implement the Strategy Pattern (provide an abstract method in the enum and override it for each constant).

I hope it might be helpful for you.

CodePudding user response：

This is solvable through a Strategy Pattern in combination with an Enum.

https://www.tutorialspoint.com/design_pattern/strategy_pattern.htm