MethodReferencesLambda.java

package examples;

import java.util.Optional;
import java.util.function.BinaryOperator;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Supplier;

public class MethodReferencesLambda {

 public static void main(String[] args) {
 // Method references is an another way of writing lambda expressions
 
 // ----------------Example 1 Function--------------
 System.out.println("Simple Lambda Function: ");
 // Functions accept one argument and produce a result.
 Function<Person, Integer> f1 = person -> person.getAge();
 // Method reference lambda (More readable) getAge need not be static method
 Function<Person, Integer> f2 = Person::getAge;
 Person p = new Person("Jack", 28);
 System.out.println(f1.apply(p));
 System.out.println(f2.apply(p));

 // ----------------Example 2 BinaryOperator-------------- 
 System.out.println("Simple Lambda BinaryOperator: ");
 // Accept two argument and produce a result.
 BinaryOperator<Integer> s1 = (i1, i2) -> Integer.sum(i1, i2);
 // Method reference lambda
 BinaryOperator<Integer> s2 = Integer::sum;
 System.out.println(s1.apply(1, 2));
 System.out.println(s2.apply(1, 2));
 
 // ----------------Example 3 Consumer-------------- 
 System.out.println("Simple Lambda Consumer: ");
 // Consumers represent operations to be performed on a single input argument.
 Consumer<String> printer1 = s -> System.out.println(s);
 // Method reference lambda
 Consumer<String> printer2 = System.out::println;
 printer1.accept("This is printer 1");
 printer2.accept("This is printer 2");

 // ----------------Example 4-------------- 
 System.out.println("Simple Lambda Supplier: ");
 //Suppliers produce a result of a given generic type
 Supplier<Person> personSupplier1 = () -> new Person();
 // Method reference lambda
 Supplier<Person> personSupplier2 = Person::new;
 System.out.println(personSupplier1.get());
 System.out.println(personSupplier2.get());
 
 // ----------------Example 5 Optional-------------- 
 System.out.println("Simple Lambda Optional: ");
 // Optionals are not functional interfaces, but nifty utilities to prevent NullPointerException
 Optional<String> o = Optional.of("bam");
 System.out.println(o.isPresent()); //true
 System.out.println(o.get()); //"bam"
 System.out.println(o.orElse("fallback")); //"bam"
 }

}