package org.example.jdk.res;
import org.example.lambda.domain.Person;
import org.junit.Test;
import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class Test01 {
/*
* Stream结果收集
* 收集到集合中
* */
@Test
public void test01(){
//Stream<String> stream = Stream.of("aa", "bb", "cc");
List<String> collect = Stream.of("aa", "bb", "cc")
.collect(Collectors.toList());
System.out.println(collect);
//收集到set集合中
Set<String> set = Stream.of("aa", "bb", "cc")
.collect(Collectors.toSet());
System.out.println(set);
//如果需要获取的类型为具体实现，比如：ArrayList，HashSet
ArrayList<String> arrayList = Stream.of("aa", "bb", "cc")
.collect(Collectors.toCollection(() -> new ArrayList<>()));
System.out.println(arrayList);
}
/*
* Stream结果收集到数组中
* */
@Test
public void test02(){
Object[] objects = Stream.of("aa", "bb", "cc","aa")
.toArray();//返回的数组中的元素是Object类型
System.out.println(objects);
//如果需要指定返回类型
String[] strings = Stream.of("aa", "bb", "cc", "aa")
.toArray(String[] :: new);
System.out.println(strings);
}
/*
* Stream流聚合
* */
@Test
public void test03(){
//获取年龄最大值
Optional<Person> collect = Stream.of(
new Person("qql", 50, 175),
new Person("ltb", 60, 156),
new Person("ldw", 20, 156)
).collect(Collectors.maxBy((p1, p2) -> p1.getAge() - p2.getAge()));
System.out.println(collect);
//获取年龄最小值
Optional<Person> c = Stream.of(
new Person("qql", 50, 175),
new Person("ltb", 60, 156),
new Person("ldw", 20, 156)
).collect(Collectors.minBy((p1, p2) -> p1.getAge() - p2.getAge()));
System.out.println(c);
//获取年龄和
Integer sum = Stream.of(
new Person("qql", 50, 175),
new Person("ltb", 60, 156),
new Person("ldw", 20, 156)
).collect(Collectors.summingInt(s -> s.getAge()));
System.out.println(sum);
}
/*
* 分组计算
* */
@Test
public void test04(){
//根据姓名分组
Map<String, List<Person>> map = Stream.of(
new Person("qql", 50, 175),
new Person("ltb", 60, 156),
new Person("ldw", 20, 156)
).collect(Collectors.groupingBy(s -> s.getName()));
map.forEach((k,v)-> System.out.println("k=" + k + "v=" + v));
//根据年龄分组
Map<Integer, List<Person>> map1 = Stream.of(
new Person("qql", 50, 175),
new Person("ltb", 60, 156),
new Person("ldw", 20, 156)
).collect(Collectors.groupingBy(s -> s.getAge()));
map1.forEach((a,b)-> System.out.println("a=" + a + "b=" + b));
}
/*
* 分区操作
* */
@Test
public void test05(){
Map<Boolean, List<Person>> tq = Stream.of(
new Person("qql", 50, 175),
new Person("ltb", 60, 156),
new Person("ldw", 20, 156)
).collect(Collectors.partitioningBy(p -> p.getAge() > 20));
tq.forEach((k,v)-> System.out.println(k+"\t"+v));
}
}
jdk8新特性对应代码
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2023-07-14
10:13:59
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jdk8.zip （53个子文件） 
jdk8 
pom.xml 1KB src test java org example jdk res Test01.java 4KB Test03.java 1KB Test02.java 1KB main resources java org example lambda DemoLambda05.java 860B DemoLambda03.java 1KB DemoLambda02.java 574B service OrderService.java 107B UserService.java 236B StudentService.java 118B DemoLambda01.java 718B domain Person.java 293B streamAPI StreamTest02.java 848B StreamTest01.java 875B StreamTest06.java 993B StreamTest.java 418B StreamTest05.java 3KB StreamTest04.java 578B StreamTest03.java 338B Optional OptionalTest03.java 404B OptionalTest04.java 1KB OptionalTest02.java 1KB OptionalTest01.java 830B .idea jarRepositories.xml 864B uiDesigner.xml 9KB workspace.xml 6KB misc.xml 544B compiler.xml 537B .gitignore 190B encodings.xml 267B target classes org example lambda DemoLambda01.class 1KB DemoLambda02$1.class 743B DemoLambda05.class 3KB DemoLambda03.class 2KB DemoLambda02.class 2KB service OrderService.class 189B StudentService.class 194B UserService.class 225B DemoLambda01$1.class 1KB domain Person.class 3KB streamAPI StreamTest01.class 2KB StreamTest02.class 3KB StreamTest06.class 3KB StreamTest04.class 2KB StreamTest05.class 2KB StreamTest03.class 913B StreamTest.class 1KB Optional OptionalTest03.class 2KB OptionalTest01.class 858B OptionalTest02.class 2KB OptionalTest04.class 3KB test-classes org example jdk res Test02.class 3KB Test01.class 7KB generated-test-sources test-annotations generated-sources annotations 资源评论
