orElse and orElseGet

Learn default values with orElse and orElseGet.

Default value: orElse

orElse(default) returns the value if present, otherwise the given default. This is the simplest way to handle an empty Optional safely.

Example: opt.orElse("Guest"). If opt is empty the result is "Guest"; if not, the inner value is returned. One caveat: the expression passed to orElse is always evaluated, even when opt is present. If it is an expensive computation this is wasteful; for such cases orElseGet is a better fit.

Lazy default: orElseGet

orElseGet(Supplier) also returns a default value; but it produces the default lazily through a Supplier. The default is computed only when the Optional is empty.

Example: opt.orElseGet(() -> fetchFromDb()). If opt is present fetchFromDb is never called; if empty, it is called. This saves performance on expensive operations compared to orElse. Because a Supplier is a function re-evaluated on each call, it is also safer in code with side effects.

Exercise Give a default to an empty Optional

Create an empty Optional<String> with Optional.empty(). Use orElse("Guest") to get the default value. Print the result with System.out.println.

Show example solution

import java.util.Optional;

public class OrElseDefault {
    public static void main(String[] args) {
        Optional<String> name = Optional.empty();
        String result = name.orElse("Guest");
        System.out.println(result);
    }
}

Test yourself

Complete the orElse call

String result = opt.____("Misafir");

Show answer

String result = opt.orElse("Misafir");

Match the orElse family

orElse

Value or default
orElseGet

Takes a Supplier
orElseThrow

Throws an error
orElse(default)

Always evaluated
Which method takes a Supplier for the default value?
- orElse
- orElseGet
- ifPresent
- orElseThrow
Show answer

orElseGet — orElseGet takes a Supplier and produces the default lazily.

Next lesson: ifPresent and isPresent

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