using orElseGet vs orElse in Java8

Question

I have a service that return a OptionalDouble, if it is null i return a value from another service, but I don't know if it is better orElseGet or orElse in terms of performance or best practices..

Option1)

fixerService.getRate(addWalletAmount.getMenuSymbol())
                                    .orElseGet(() -> menuService
                                                    .findBySymbol(addWalletAmount
                                                            .getMenuSymbol())   
                                                            .getPrice()
                                                            .doubleValue());

Option2)

 fixerService.getRate(addWalletAmount.getMenuSymbol())
                                    .orElse(menuService
                                                    .findBySymbol(addWalletAmount
                                                            .getMenuSymbol())   
                                                            .getPrice()
                                                            .doubleValue());

score 2 · Accepted Answer · answered Nov 11 '18 at 11:45

Of course orElseGet() is preferable. orElse() would execute your service even when the OptionalDouble is not empty, which is wasteful (since menuService.findBySymbol(addWalletAmount.getMenuSymbol()).getPrice().doubleValue() is the argument passed to the orElse() method, and it must be evaluated before orElse() is executed).

orElseGet() would only execute your service if the OptionalDouble is empty.

using orElseGet vs orElse in Java8

1 Answers1