In a piece of Java code I inherited, I encountered the following what seems to be a Lambda expression:
id ->""
Appearing as a parameter to a method:
runner.setIntanceName(id ->"")
I consulted the Lambda Expressions documentation but could not find the meaning of this special expression.
What does id ->"" mean?
E.g. you have:
public static void setIntanceName(Function<String, String> function) {
function.apply("aaa");
}
Then to use this method: setIntanceName(id -> "") or
setIntanceName(new Function<String, String>() {
@Override
public String apply(String id) {
return "";
}
});
I.e. you add a function to the method (or treat it as instance of some interface with only one method - it is called functional interface). Method setIntanceName will use this function. In given example, this function accepts id=aaa and returns always empty string as function's result.
(id -> "") means is: "Accept any string as a parameter but always return an empty string"?The left side specifies the parameters required by the expression, which could also be empty if no parameters are required.
The right side is the lambda body which specifies the actions of the lambda expression.
so here id ->"" id is empty string.
read more about it here
I think that person, who have written that intended to ignore any id-arguments and return just an empty string.
-> is just the token that separates the parameters from the body. See the part Syntax of Lambda Expressions in the very documentation you linked to https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html
"" is the body. In this case, a constant empty string.
idbecomes""