Stream Lombok 연습 예제

import lombok.AllArgsConstructor;
import lombok.Data;

import java.math.BigDecimal;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import static java.util.stream.Collectors.*;

public class Hello {
    public static void main(String[] args) {
        final List<Product> products = Arrays.asList(
                new Product(1L,"A",new BigDecimal("100.50")),
                new Product(2L,"B",new BigDecimal("90.10")),
                new Product(3L,"C",new BigDecimal("70.80")),
                new Product(4L,"D",new BigDecimal("80.60")),
                new Product(5L,"E",new BigDecimal("50.55"))
        );

        List<Product> upperThirty = products.stream()
                .filter(product -> product.getPrice().compareTo(new BigDecimal("80")) >= 0)
                .sorted(new Comparator<Product>() {
                    @Override
                    public int compare(Product o1, Product o2) {
                        return o1.getPrice().compareTo(o2.getPrice());
                    }
                })
                .collect(toList());
        System.out.println("upperThirty: \n"+upperThirty);
        System.out.println("==========================");

        String upperThirtyString = products.stream()
                .filter(product -> product.getPrice().compareTo(new BigDecimal("80")) >= 0)
                .map(i -> i.toString())
                .collect(joining("\n"));

        System.out.println("upperThirtyString: \n"+upperThirtyString);
        System.out.println("==========================");

        BigDecimal sumValue = products.stream()
                                    .map(product -> product.getPrice())
                                    .reduce(BigDecimal.ZERO, (a,b) ->
                                            a.add(b));
        System.out.println("sumValue :" + sumValue);

        OrderedItem orderedItem1 = new OrderedItem(1L,products.get(0),5);
        OrderedItem orderedItem2 = new OrderedItem(2L,products.get(1),3);
        OrderedItem orderedItem3 = new OrderedItem(3L,products.get(2),4);
        OrderedItem orderedItem4 = new OrderedItem(4L,products.get(3),1);
        OrderedItem orderedItem5 = new OrderedItem(5L,products.get(4),0);
        Order order = new Order(1L,Arrays.asList(orderedItem1,orderedItem2,orderedItem3,orderedItem4,orderedItem5));
        System.out.println("TotalPrice" + order.totalPrice());
    }
}

@AllArgsConstructor
@Data
class Product{
    private Long id;
    private String name;
    private BigDecimal price;
}

@AllArgsConstructor
@Data
class OrderedItem{
    private Long id;
    private Product product;
    private int quantitiy;

    public BigDecimal getTotalPrice(){
        return product.getPrice().multiply(new BigDecimal(quantitiy));
    }
}

@AllArgsConstructor
@Data
class Order{
    private Long id;
    private List<OrderedItem>items;

    public BigDecimal totalPrice(){
        return items.stream()
                    .map(item -> item.getTotalPrice())
                    .reduce(BigDecimal.ZERO,BigDecimal::add);
    }
}