I need to compare an array of objects by one property of one of its objects property.
I am doing :
List<Sell> collect = sells.stream()
.sorted(Comparator.comparing(Sell::getClient.name, String::compareToIgnoreCase))
.collect(Collectors.toList());
It's not compiling, doesn anyone know how to do?
Thanks.
This is the part of the code that causes an error
Sell::getClient.name
Your can create a reference to a (static or non-static) method of an arbitrary object of a particular type. A reference to the getClient method of any object of Sell type looks like this :
Sell::getClient
But method references are not objects and don't have members to access. With this code you are trying to access a member variable of the reference (and can't)
Sell::getClient.name
Also, method references are not classes so you can't get another method reference from them. You couldn't do something like that if you tried :
Sell::getClient::getName
Correct syntax for your particular case was provided by @mlk :
x -> x.getClient().nameSell::getClientName (doesn't have to be a static method)In order to access the nested property and sort in reversed order, I am doing as:
Comparator<Sell> comparator = Comparator.comparing(h -> h.getAudit().getCreatedTs());
sells.sort(comparator.reversed());
Sell.sort((Comparator.comparing(x -> x.getAudit().getCreatedTs()).reversed()); but kept having an error on the reversed methodI can't see your code, or the error you are getting. So this is a guess.
I believe you want
class Test {
// I assume that Client looks like this.
static class Client {
public String name;
}
// And that Sell looks like this.
// I'm sure your Client and Sell are bigger, but this is all
// that matters for now.
static class Sell {
public Client getClient() { return null; }
}
public static void main (String[] args) throws java.lang.Exception
{
List<Sell> sells = new ArrayList<>();
sells.stream().sorted(Comparator.comparing(x -> x.getClient().name, String::compareToIgnoreCase))
}
}
You want to call a method on the return of that, so you need to create an anonymous function.
Your other option would be:
static class Sell {
public String getClientName() { return null; }
}
// ...
sells.stream().sorted(Comparator.comparing(Sell::getClientName, String::compareToIgnoreCase))
getClientName is available, it doesn't have to be static. According to the tutorial you can get a "Reference to an instance method of an arbitrary object of a particular type"
ComparatoruseString.CASE_INSENSITIVE_ORDER.String::compareToIgnoreCaseis a comparison method returning an int not aComparator