Java reference

Optional.orElseGet()

Returns the value, or calls a function to create a fallback.

Available since: Java 8

Syntax

T orElseGet(Supplier<? extends T> supplier)

Parameters

Parameter	Type	Description
supplier	Supplier<? extends T>	A function that creates the fallback value.

Return value

TThe value from the `Optional`, or the result of `supplier`.

Examples

The function is called only when the value is absent:

String loadDefault() {
    IO.println("loading default...");
    return "default";
}
 
void main() {
    IO.println(Optional.of("cached").orElseGet(this::loadDefault));
    IO.println(Optional.<String>empty().orElseGet(this::loadDefault));
}

Output:

cached
loading default...
default

Notes

The difference from orElse() shows when creating the fallback is expensive or has side effects: orElseGet() calls the function only for an empty Optional.

In the tutorial

Optional — The Optional class in Java: a value that may be absent, creating it with of and empty, orElse, map, ifPresent and orElseThrow.

Thanks for reading!