"Predicate" entries
Java 8 functional interfaces
Getting to know various out-of-the-box functions such as Consumer, Predicate, Supplier
In the first part of this series, we learned that lambdas are a type of functional interface – an interface with a single abstract method. The Java API has many one-method interfaces such as Runnable, Callable, Comparator, ActionListener and others. They can be implemented and instantiated using anonymous class syntax. For example, take the ITrade functional interface. It has only one abstract method that takes a Trade object and returns a boolean value – perhaps checking the status of the trade or validating the order or some other condition.
@FunctionalInterface
public interface ITrade {
public boolean check(Trade t);
}In order to satisfy our requirement of checking for new trades, we could create a lambda expression, using the above functional interface, as shown here:
ITrade newTradeChecker = (Trade t) -> t.getStatus().equals("NEW");
// Or we could omit the input type setting:
ITrade newTradeChecker = (t) -> t.getStatus().equals("NEW");