Java8InAction_Chapter01

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Collectors;

/**
 * 在这里编写类的功能描述
 *
 * @author shangjinyu
 * @created 2017/9/29
 */
public class Notes {

    //构造一个待筛选的list
    List<Apple> inventory = Arrays.asList(new Apple(80, "green"),
            new Apple(155, "green"),
            new Apple(120, "red"));

    //找出list中的所有的绿色苹果
    //写法一
    public List<Apple> filterGreenApples(List<Apple> inventory) {
        List<Apple> result = new ArrayList<>();
        for (Apple apple : inventory) {
            if (apple.getColor().equals("green")) {
                result.add(apple);
            }
        }
        return result;
    }

    List<Apple> greenApples1 = filterGreenApples(inventory);

    /*
    public interface Predicate<T>{
        boolean test(T t);
    }
    一个java8中的函数FunctionInterface接口
    */
    
    //写法二

    public List<Apple> filterGreenApples(List<Apple> inventory, Predicate<Apple> p) {
        List<Apple> result = new ArrayList<>();
        for (Apple apple : inventory) {
            if (p.test(apple)) {
                result.add(apple);
            }
        }
        return result;
    }

    //用法
    List<Apple> greenApples2 = filterGreenApples(inventory, new Predicate<Apple>() {
        @Override
        public boolean test(Apple apple) {
            return apple.getColor().equals("green");
        }
    });
    
    
    public boolean isGreenApple(Apple apple) {
        return apple.getColor().equals("green");
    }
    
    //lambdasin写法
    List<Apple> greenApples3 = filterGreenApples(inventory, this::isGreenApple);
    List<Apple> greenApples4 = filterGreenApples(inventory, (Apple apple) -> apple.getColor().equals("green"));
    List<Apple> greenApples5 = filterGreenApples(inventory, item -> item.getColor().equals("green"));
    //流
    //顺序处理
    List<Apple> greenApples6 = inventory.stream().filter(apple -> apple.getColor().equals("green")).collect(Collectors.toList());
    //并行处理
    List<Apple> greenApples7 = inventory.parallelStream().filter(apple -> apple.getColor().equals("green")).collect(Collectors.toList());

    //一个实体类
    public class Apple {
        private int weight = 0;
        private String color = "";

        public Apple(int weight, String color) {
            this.weight = weight;
            this.color = color;
        }

        public Integer getWeight() {
            return weight;
        }

        public void setWeight(Integer weight) {
            this.weight = weight;
        }

        public String getColor() {
            return color;
        }

        public void setColor(String color) {
            this.color = color;
        }

        public String toString() {
            return "Apple{" +
                    "color='" + color + '\'' +
                    ", weight=" + weight +
                    '}';
        }
    }
}