Java8 Stream常用操作

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;

@Data
@AllArgsConstructor
@Builder
public class Fruit {
    private Integer id;
    private String name;
    private Double money;
    private Integer num;
}

测试用例

import org.junit.Before;
import org.junit.Test;

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

public class FruitTest {
    List<Fruit> fruitList = null;
    
    @Before
    public void setup() {
        fruitList = new ArrayList<>();
        fruitList.add(new Fruit(1, "Apple1", 4.5, 11));
        fruitList.add(new Fruit(1, "Apple2", 3.1, 2));
        fruitList.add(new Fruit(2, "Banana", 4.89, 8));
        fruitList.add(new Fruit(3, "Pear", 10.99, 9));
    }

    @Test
    public void testGroupBy() {
        System.out.println("testGroupBy()");
        Map<Integer, List<Fruit>> map = fruitList.stream()
                .collect(Collectors.groupingBy(Fruit::getId));
        System.out.println(map);
    }

    @Test
    public void testListToMap() {
        System.out.println("testListToMap()");
        Map<Integer, Fruit> map = fruitList.stream()
                .collect(Collectors.toMap(Fruit::getId, a -> a, (k1, k2) -> k1));
        System.out.println(map);
    }

    @Test
    public void testFilter() {
        System.out.println("testFilter()");
        List<Fruit> ls = fruitList.stream()
                .filter(a -> a.getName().equals("香蕉"))
                .collect(Collectors.toList());
        System.out.println(ls);
    }

    @Test
    public void testMaxMin() {
        System.out.println("testSum()");
        Optional<Fruit> max = fruitList.stream().max(Comparator.comparingDouble(Fruit::getMoney));
        max.ifPresent(System.out::println);
        Optional<Fruit> min = fruitList.stream().min(Comparator.comparingDouble(Fruit::getMoney));
        min.ifPresent(System.out::println);
    }

标签：常用,Stream,System,public,fruitList,println,Fruit,Java8,out
来源： https://blog.csdn.net/qq_21009627/article/details/113799179