I have the following method
public static Boolean test(String str, Optional<Boolean> test) {
}
but if I try to call it like
test("hello")
I get an error that the method requires two parameters.
Shouldn't the Optional parameter allow to me call the test method without providing the Optional parameter?
Optional is not a optional parameter as var-args is.
Optional is a container object which may or may not contain a non-null value.
So you could invoke the method as :
test("...", Optional.of(true));
or
test("...", Optional.empty());
Note that with var-args :
public static Boolean test(String str, Boolean... test) {
//...
}
this would be valid :
test("hello")
But var-args is not the correct way to pass an optional parameter as it conveys 0 or more objects and not 0 or 1 object.
Method overload is better :
public static Boolean test(String str, Boolean test) {
// ...
}
public static Boolean test(String str) {
// ...
}
In some other cases, the @Nullable constraints (JSR-380) may also be interesting.
... means 0 or more, which makes test a Boolean[] and more than 1 Boolean can be passed into this method.
@Nullable may be a good alternative too.In short, no.
Optional is a class and in Java you must pass the exact number of parameters to a method just like it is defined.
The only exception is when you put ... after the class object name in the method declaration.
public String test (String X, String... Y) { }
Which makes the second parameter be either zero or more.
Optional is a class like any other. It is not defined in the language specification, and thus it is not handled in any way that is special.Try this
public static Boolean test(String str, Boolean ... test) {}
it will work with you
test("hello", Optional.empty());- -Optionalis a poor substitute for overloading.Optionalmeans here.Optionalis another type of Java object...