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Why does the below code return Predicate<String> and not boolean?
My understanding is that the !s.isEmpty() check here is going against the Predicate boolean test(T t); The return type here is boolean.
So in my lambda should my nonEmptyStringPredicate not be of type boolean? Obviously, it's not, I'm just trying to understand why it's not.
Predicate<String> nonEmptyStringPredicate = (String s) -> !s.isEmpty();
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Predicate<T> is a generic functional interface that represents a single argument function that returns a boolean value (true or false). This interface available in java. util. function package and contains a test(T t) method that evaluates the predicate of a given argument.
Predicate on the other hand is just a FunctionalInterface , that you've represented using a lambda expression.
The predicate is a predefined functional interface in Java defined in the java. util. Function package. It helps with manageability of code, aids in unit-testing, and provides various handy functions.
Interface Predicate<T> Functional Interface: This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference. Represents a predicate (boolean-valued function) of one argument.
If you really are willing to get a boolean though from the Predicate, you can use its test method:
Predicate<String> nonEmptyStringPredicate = s -> !s.isEmpty();
boolean val = nonEmptyStringPredicate.test("any"); // true
Predicate on the other hand is just a FunctionalInterface, that you've represented using a lambda expression.
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