assertj how to check in a list that a property is greather than a value - assertj

Question

Given:
class Point {
int x;
int y;
}
List<Point> points;
How can I check that property x in a list of Points is greather than a value? I aim something similar to:
assertThat(points).extracting("x").isGreatherThan(20)
However I can't find 'isGreatherThan' after 'extracting'
Update
I don't aim writing custom conditions for this kind of value checking, as assertj already has methods for checking numbers.
Thanks

Answer 1

You can use filteredOn as it supports java 8 Predicate, e.g:
assertThat(listOfPoints).filteredOn(p -> p.x > 20).isNotEmpty();
If you want to do more complex stuff, using Condition is the way to go, in AssertJ 3.x they are simpler to write, rewriting Florian Schaetz example:
Condition<Integer> greaterThan20 = new Condition<>(v -> v.intValue() > 20, "greater than 20");

Answer 2

You can try this one...
.extracting( "x", Integer.class ).areAtLeast( 1, greaterThan20 );
Of course you'll have to write the condition yourself, something like...
final Condition<Integer> greaterThan20 = new Condition<Integer>("greater than 20") {
#Override
public boolean matches(Integer value) {
return value.intValue() > 20;
}
};

Answer 3

In Java 8 you can do something like this:
assertThat(listOfPoints.stream().filter(p->p.x > 20).toArray()).hasSameSizeAs(listOfPoints);
That's for the case where you want ALL points to have x > 20.
To verify that there's at least one (as in Florian Schaetz's answer):
assertThat(listOfPoints.stream().filter(p->p.x > 20).toArray()).isNotEmpty();