stream流的統計demo

Stream流簡單demo，直接獲取list集合的相關數據

/**
 * 
 */
package lambda;

import java.util.ArrayList;
import java.util.DoubleSummaryStatistics;
import java.util.List;

/**
 * @author Administrator
 *
 */
public class StreamDemo {
    public static void main(String[] args) {
        List<Order> list = new ArrayList<>();
        list.add(new Order("西瓜", 2.8, 100));
        list.add(new Order("蘋果", 8.8, 100));
        list.add(new Order("芒果", 12.8, 100));
        list.add(new Order("葡萄", 9.8, 100));

        // Stream<Order> stream = list.stream();
        DoubleSummaryStatistics statistics
            = list.stream().mapToDouble(((obj) -> obj.getAmount() * obj.getPrice())).summaryStatistics();
        System.out.println("訂單均值：" + statistics.getAverage());
        System.out.println("訂單最大值：" + statistics.getMax());
        System.out.println("訂單最小值：" + statistics.getMin());
        System.out.println("訂單總數：" + statistics.getCount());
        System.out.println("訂單總額：" + statistics.getSum());
    }
}

/**
 * 虛擬訂單
 */
class Order {
    // 訂單名稱
    private String title;
    // 訂單價格
    private Double price;
    // 訂單數量
    private int amount;

    /**
     * @return the title
     */
    public String getTitle() {
        return title;
    }

    /**
     * @param title the title to set
     */
    public void setTitle(String title) {
        this.title = title;
    }

    /**
     * @return the price
     */
    public Double getPrice() {
        return price;
    }

    /**
     * @param price the price to set
     */
    public void setPrice(Double price) {
        this.price = price;
    }

    /**
     * @return the amount
     */
    public int getAmount() {
        return amount;
    }

    /**
     * @param amount the amount to set
     */
    public void setAmount(int amount) {
        this.amount = amount;
    }

    public Order(String title, Double price, int amount) {
        this.title = title;
        this.price = price;
        this.amount = amount;
    }
}