Predefined functional interfaces

• Previous examples used manually defined functional interfaces to illustrate the basic concepts.

• However, JDK 8 introduced the java.util.function package, which provides predefined functional interfaces for ease of use.

java.util.function package

• Offers several ready-to-use functional interfaces.

• Reduces the need to create custom interfaces.

Benefits

• Simplifies development.

• Standardizes the use of functional interfaces in projects.

• Facilitates integration with modern Java APIs.

Using the Predicate Interface

• Defines an abstract method called test(T val).

• Returns true if the value meets a specific condition or restriction.

Example of Usage

• Implements a lambda expression to check if a number is even.

• The lambda expression is assigned to an object of type Predicate.

Working of the test Method

• Evaluates the value provided as an argument.

• Returns true if the number is even, otherwise returns false.

Benefit

• Allows you to use dynamic conditions in a simple and reusable way in lambda expressions.

// Uses the internal Predicate functional interface.
// Import the Predicate interface.
import java.util.function.Predicate;
class UsePredicateInterface {
public static void main(String args[])
{
// This lambda expression uses Predicate for
// determine if a number is even.
Predicate isEven = (n) -> (n %2) == 0;
if(isEven.test(4)) System.out.println("4 is even");
if(!isEven.test(5)) System.out.println("5 is odd");
}
}

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