I have a String as "ishant" and a Set<String> as ["Ishant", "Gaurav", "sdnj"] . I need to write the Predicate for this. I have tried as below code, but it is not working
Predicate<Set<String>,String> checkIfCurrencyPresent = (currencyList,currency) -> currencyList.contains(currency);
How can I create a Predicate which will take Set<String> and String as a parameter and can give the result?
A Predicate<T> which you're currently using represents a predicate (boolean-valued function) of one argument.
You're looking for a BiPredicate<T,U> which essentially represents a predicate (boolean-valued function) of two arguments.
BiPredicate<Set<String>,String> checkIfCurrencyPresent = (set,currency) -> set.contains(currency);
or with method reference:
BiPredicate<Set<String>,String> checkIfCurrencyPresent = Set::contains;
If you were to stick with using Predicate, use something similar as :
Set<String> currencies = Set.of("Ishant", "Gaurav", "sdnj");
String input = "ishant";
Predicate<String> predicate = currencies::contains;
System.out.print(predicate.test(input)); // prints false
The primary difference between the BiPredicate and Predicate would be their test method implementation. A Predicate would use
public boolean test(String o) {
return currencies.contains(o);
}
and a BiPredicate would instead use
public boolean test(Set<String> set, String currency) {
return set.contains(currency);
}
Aomine's answer is complete. using of BiFunction<T, U, R> is another way:
BiFunction<Set<String>,String,Boolean> checkIfCurrencyPresent = Set::contains;