LambdaJ: why can't we apply operation in select clause?
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24-06-2021 - |
Frage
select(list, having(on(Integer.class).intValue() % 2, equalTo(0)));
the code above throws exception.
Lösung
The %
operation has to be evaluated before select() whereas what you want it to be evaluated for each entry. i.e. what you want is closures which is available in Java 8.
If you were using a loop you could write
for(int i: list)
if(i % 2 == 0)
// do something with i.
Java's syntax often makes using a loop the cleanest solution when ideally you should have a choice (its also a lot faster).
Andere Tipps
You'll want to define your own matcher:
Matcher<Integer> even = new Predicate<Integer>() {
public boolean apply(Integer item) {
return item % 2 == 0;
} };
Adapted from:http://code.google.com/p/lambdaj/wiki/LambdajFeatures
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