Java Stream API demo

StreamDemo.java

package com.obomprogramador.stream;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class StreamDemo {
	
	public static void main(String[] args) {
		
		List<Double> valores = new ArrayList<Double>(Arrays.asList(1.45,2.10,2.10,3.67));
		Stream<Double> stNumeros = valores.stream(); 
		
		// Imprimindo: O Stream é de uso único
		System.out.println(stNumeros); // Não funciona
		stNumeros.forEach(s -> System.out.println(s));
		//stNumeros.forEach(System.out::println); // Erro: stream has already been closed
		
		// Usando Supplier: Podemos usar a sintaxe "double colon" para invocar métodos em Lambda
		Supplier<Stream<Double>> stSup = () -> Stream.of(valores.toArray(Double[]::new));
		stSup.get().forEach(s -> System.out.println(s));
		stSup.get().forEach(System.out::println);
		
		// Filter:
		stSup.get().filter(v -> v < 3).forEach(System.out::println);
		
		// Map:
		List<Float> flist = stSup.get().map(v -> v.floatValue()).collect(Collectors.toList());
		System.out.println(flist.get(1).getClass().getName());
		
		// Distinct: 
		stSup.get().distinct().forEach(System.out::println);
		
		// Reduce:
		System.out.println(stSup.get().reduce((x,y) -> x*y));
	}

}