Java Function Functional Interface Example

A Function is a functional interface whose sole purpose is to return any result by working on a single input argument.

A Function interface represents a function that accepts one argument and returns a result.

Java Function Functional Interface Example

The following example demonstrates:
1. Convert centigrade to Fahrenheit
2. Convert String to Integer
3. Convert PersonEntity to PersonDTO

import java.util.function.Function; public class FunctionExample { public static void main(String[] args) { // convert centigrade to fahrenheit Function<Integer,Double> centigradeToFahrenheitInt = x -> new Double((x*9/5)+32); System.out.println("Centigrade to Fahrenheit: "+centigradeToFahrenheitInt.apply(100)); // String to an integer Function<String, Integer> stringToInt = x -> Integer.valueOf(x); System.out.println(" String to Int: " + stringToInt.apply("4")); // convert person entity to person DTO.  Function<PersonEntity, PersonDTO> function = (entity) -> { return new PersonDTO(entity.getName(), entity.getAge()); }; PersonDTO personDTO = function.apply(new PersonEntity("ramesh", 20)); System.out.println(personDTO.getName()); System.out.println(personDTO.getAge()); } } class PersonEntity { private String name; private int age; public PersonEntity(String name, int age) { super(); this.name = name; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } } class PersonDTO { private String name; private int age; public PersonDTO(String name, int age) { super(); this.name = name; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }
Output:
Centigrade to Fahrenheit: 212.0 String to Int: 4 ramesh 20

Reference


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