Java 8 Stream Collectors Snippet

StreamCollectors.java

	Car car1 = new Car("BMW","Red", 35000d);
	Car car2 = new Car("BMW","Green", 35500d);
	Car car3 = new Car("Ford","Yellow", 25000d);
	Car car4 = new Car("Toyota","Red", 10000d);

	//populate car model list whose have red values
	List<String> redCars = Stream.of(car1, car2, car3, car4)
				      .filter(s -> s.getColor().equals("Red") ) //get all cars with red values
				      .map(c -> c.getModel()) //map to get the model only
			              .collect(Collectors.toList());
	System.out.println(redCars); //Output: [BMW, Toyota]

	//group car by its model
	Map<String, List<Car>> carByModel = 
			Stream.of(car1, car2, car3, car4)
			       .collect(Collectors.groupingBy(c -> c.getModel()));
	carByModel.forEach(
	    (model, car) -> System.out.format("Model %s: %s\n", model, car) );
	/*Output:
	   Model Toyota: [Car (model=Toyota, color=Red)]
	   Model Ford: [Car (model=Ford, color=Yellow)]
	   Model BMW: [Car (model=BMW, color=Red), Car (model=BMW, color=Green)]
	*/

	//get average price for all cars
	Double averagePrice = 
		  Stream.of(car1, car2, car3, car4)
			.collect(Collectors.averagingDouble( c -> c.getPrice() )); 
	System.out.println(averagePrice); //output: 26375.0

	//Get the price summary statistics
	DoubleSummaryStatistics stats = 
		Stream.of(car1, car2, car3, car4)
			.collect(Collectors.summarizingDouble( c -> c.getPrice() )); 
	System.out.println(stats);//output: DoubleSummaryStatistics{count=4, sum=105500.000000, min=10000.000000, average=26375.000000, max=35500.000000}