Browse Source

工作中常用的一些Stream流操作~

pull/2/head
马府强 2 years ago
parent
commit
1772e9cf39
  1. 33
      streamdemo/.gitignore
  2. 11
      streamdemo/README.md
  3. 72
      streamdemo/pom.xml
  4. 13
      streamdemo/src/main/java/com/example/demo/DemoRequestScopeApplication.java
  5. 172
      streamdemo/src/main/java/com/example/demo/service/TestMain.java
  6. 1
      streamdemo/src/main/resources/application.properties
  7. 21
      streamdemo/src/main/resources/application.yml
  8. 172
      streamdemo/src/test/java/com/example/demo/testscope/TestMain.java

33
streamdemo/.gitignore

@ -0,0 +1,33 @@
HELP.md
target/
!.mvn/wrapper/maven-wrapper.jar
!**/src/main/**/target/
!**/src/test/**/target/
### STS ###
.apt_generated
.classpath
.factorypath
.project
.settings
.springBeans
.sts4-cache
### IntelliJ IDEA ###
.idea
*.iws
*.iml
*.ipr
### NetBeans ###
/nbproject/private/
/nbbuild/
/dist/
/nbdist/
/.nb-gradle/
build/
!**/src/main/**/build/
!**/src/test/**/build/
### VS Code ###
.vscode/

11
streamdemo/README.md

@ -0,0 +1,11 @@
# demo-request-scope
《基于ThreadLocal实现一个上下文管理组件》技术博客对应源码
https://juejin.cn/post/7153287656624324638
本文基于`ThreadLocal`原理,实现了一个上下文状态管理组件`Scope`,通过开启一个自定义的`Scope`,在`Scope`范围内,可以通过`Scope`各个方法读写数据;
通过自定义线程池实现上下文状态数据的线程间传递;
提出了一种基于`Filter`和`Scope`的`Request`粒度的上下文管理方案。

72
streamdemo/pom.xml

@ -0,0 +1,72 @@
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.7.4</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo-request-scope</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo-request-scope</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>30.1-jre</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-aop</artifactId>
</dependency>
<!-- 若使用redisson作为分布式锁底层,则需要引入 -->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>lock4j-redisson-spring-boot-starter</artifactId>
<version>2.2.4</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

13
streamdemo/src/main/java/com/example/demo/DemoRequestScopeApplication.java

@ -0,0 +1,13 @@
package com.example.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoRequestScopeApplication {
public static void main(String[] args) {
SpringApplication.run(DemoRequestScopeApplication.class, args);
}
}

172
streamdemo/src/main/java/com/example/demo/service/TestMain.java

@ -0,0 +1,172 @@
package com.example.demo.service;
import lombok.AllArgsConstructor;
import lombok.Data;
import org.junit.Test;
import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class TestMain {
//工作中常用的一些Stream流操作,多年实践总结
/**
* 演示map的用途一对一转换
*/
@Test
public void stringToIntMap() {
List<String> ids = Arrays.asList("205", "105", "308", "469", "627", "193", "111");
// 使用流操作
List<User> results = ids.stream()
.map(id -> {
User user = new User(Integer.valueOf(id));
return user;
})
.collect(Collectors.toList());
System.out.println(results);
}
/**
* 演示map的用途一对多转换
*/
@Test
public void stringToIntFlatmap() {
List<String> sentences = Arrays.asList("hello world", "Jia Gou Wu Dao");
// 使用流操作
List<String> results = sentences.stream()
.flatMap(sentence -> Arrays.stream(sentence.split(" ")))
.collect(Collectors.toList());
System.out.println(results);
}
/**
*filtersorteddistinctlimit
*/
@Test
public void testGetTargetUsers() {
List<String> ids = Arrays.asList("205", "10", "308", "49", "627", "193", "111", "193");
// 使用流操作
List<User> results = ids.stream()
.filter(s -> s.length() > 2)
.distinct()
.map(Integer::valueOf)
.sorted(Comparator.comparingInt(o -> o))
.limit(3)
.map(id -> new User(id))
.collect(Collectors.toList());
System.out.println(results);
}
/**
* 简单结果终止方法
*/
@Test
public void testSimpleStopOptions() {
List<String> ids = Arrays.asList("205", "10", "308", "49", "627", "193", "111", "193");
// 统计stream操作后剩余的元素个数
System.out.println(ids.stream().filter(s -> s.length() > 2).count());
// 判断是否有元素值等于205
System.out.println(ids.stream().filter(s -> s.length() > 2).anyMatch("205"::equals));
// findFirst操作
ids.stream().filter(s -> s.length() > 2)
.findFirst()
.ifPresent(s -> System.out.println("findFirst:" + s));
}
/**
* 一旦一个Stream被执行了终止操作之后后续便不可以再读这个流执行其他的操作了否则会报错
*/
@Test
public void testHandleStreamAfterClosed() {
List<String> ids = Arrays.asList("205", "10", "308", "49", "627", "193", "111", "193");
Stream<String> stream = ids.stream().filter(s -> s.length() > 2);
// 统计stream操作后剩余的元素个数
System.out.println(stream.count());
System.out.println("-----下面会报错-----");
// 判断是否有元素值等于205
try {
System.out.println(stream.anyMatch("205"::equals));
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("-----上面会报错-----");
}
/**
* 生成集合
*/
@Test
public void testCollectStopOptions() {
List<User> ids = Arrays.asList(new User(17), new User(22), new User(23));
// collect成list
List<User> collectList = ids.stream().filter(dept -> dept.getId() > 20)
.collect(Collectors.toList());
System.out.println("collectList:" + collectList);
// collect成Set
Set<User> collectSet = ids.stream().filter(dept -> dept.getId() > 20)
.collect(Collectors.toSet());
System.out.println("collectSet:" + collectSet);
// collect成HashMap,key为id,value为Dept对象
Map<Integer, User> collectMap = ids.stream().filter(dept -> dept.getId() > 20)
.collect(Collectors.toMap(User::getId, dept -> dept));
System.out.println("collectMap:" + collectMap);
}
/**
* 生成拼接字符串
*/
@Test
public void testCollectJoinStrings() {
List<String> ids = Arrays.asList("205", "10", "308", "49", "627", "193", "111", "193");
String joinResult = ids.stream().collect(Collectors.joining(","));
System.out.println("拼接后:" + joinResult);
}
/**
* 数学运算
*/
@Test
public void testNumberCalculate() {
List<Integer> ids = Arrays.asList(10, 20, 30, 40, 50);
// 计算平均值
Double average = ids.stream().collect(Collectors.averagingInt(value -> value));
System.out.println("平均值:" + average);
// 数据统计信息
IntSummaryStatistics summary = ids.stream().collect(Collectors.summarizingInt(value -> value));
System.out.println("数据统计信息: " + summary);
}
}
@Data
@AllArgsConstructor
class User {
private int id;
}

1
streamdemo/src/main/resources/application.properties

@ -0,0 +1 @@

21
streamdemo/src/main/resources/application.yml

@ -0,0 +1,21 @@
spring:
redis:
database: 0
# Redis服务器地址 写你的ip
host: 192.168.56.10
# Redis服务器连接端口
port: 6379
# Redis服务器连接密码(默认为空)
password: 123456
# 连接池最大连接数(使用负值表示没有限制 类似于mysql的连接池
jedis:
pool:
max-active: 200
# 连接池最大阻塞等待时间(使用负值表示没有限制) 表示连接池的链接拿完了 现在去申请需要等待的时间
max-wait: -1
# 连接池中的最大空闲连接
max-idle: 10
# 连接池中的最小空闲连接
min-idle: 0
# 连接超时时间(毫秒) 去链接redis服务端
timeout: 6000

172
streamdemo/src/test/java/com/example/demo/testscope/TestMain.java

@ -0,0 +1,172 @@
package com.example.demo.testscope;
import lombok.AllArgsConstructor;
import lombok.Data;
import org.junit.jupiter.api.Test;
import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class TestMain {
//工作中常用的一些Stream流操作,多年实践总结
/**
* 演示map的用途一对一转换
*/
@Test
public void stringToIntMap() {
List<String> ids = Arrays.asList("205", "105", "308", "469", "627", "193", "111");
// 使用流操作
List<User> results = ids.stream()
.map(id -> {
User user = new User(Integer.valueOf(id));
return user;
})
.collect(Collectors.toList());
System.out.println(results);
}
/**
* 演示map的用途一对多转换
*/
@Test
public void stringToIntFlatmap() {
List<String> sentences = Arrays.asList("hello world", "Jia Gou Wu Dao");
// 使用流操作
List<String> results = sentences.stream()
.flatMap(sentence -> Arrays.stream(sentence.split(" ")))
.collect(Collectors.toList());
System.out.println(results);
}
/**
*filtersorteddistinctlimit
*/
@Test
public void testGetTargetUsers() {
List<String> ids = Arrays.asList("205", "10", "308", "49", "627", "193", "111", "193");
// 使用流操作
List<User> results = ids.stream()
.filter(s -> s.length() > 2)
.distinct()
.map(Integer::valueOf)
.sorted(Comparator.comparingInt(o -> o))
.limit(3)
.map(id -> new User(id))
.collect(Collectors.toList());
System.out.println(results);
}
/**
* 简单结果终止方法
*/
@Test
public void testSimpleStopOptions() {
List<String> ids = Arrays.asList("205", "10", "308", "49", "627", "193", "111", "193");
// 统计stream操作后剩余的元素个数
System.out.println(ids.stream().filter(s -> s.length() > 2).count());
// 判断是否有元素值等于205
System.out.println(ids.stream().filter(s -> s.length() > 2).anyMatch("205"::equals));
// findFirst操作
ids.stream().filter(s -> s.length() > 2)
.findFirst()
.ifPresent(s -> System.out.println("findFirst:" + s));
}
/**
* 一旦一个Stream被执行了终止操作之后后续便不可以再读这个流执行其他的操作了否则会报错
*/
@Test
public void testHandleStreamAfterClosed() {
List<String> ids = Arrays.asList("205", "10", "308", "49", "627", "193", "111", "193");
Stream<String> stream = ids.stream().filter(s -> s.length() > 2);
// 统计stream操作后剩余的元素个数
System.out.println(stream.count());
System.out.println("-----下面会报错-----");
// 判断是否有元素值等于205
try {
System.out.println(stream.anyMatch("205"::equals));
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("-----上面会报错-----");
}
/**
* 生成集合
*/
@Test
public void testCollectStopOptions() {
List<User> ids = Arrays.asList(new User(17), new User(22), new User(23));
// collect成list
List<User> collectList = ids.stream().filter(dept -> dept.getId() > 20)
.collect(Collectors.toList());
System.out.println("collectList:" + collectList);
// collect成Set
Set<User> collectSet = ids.stream().filter(dept -> dept.getId() > 20)
.collect(Collectors.toSet());
System.out.println("collectSet:" + collectSet);
// collect成HashMap,key为id,value为Dept对象
Map<Integer, User> collectMap = ids.stream().filter(dept -> dept.getId() > 20)
.collect(Collectors.toMap(com.example.demo.testscope.User::getId, dept -> dept));
System.out.println("collectMap:" + collectMap);
}
/**
* 生成拼接字符串
*/
@Test
public void testCollectJoinStrings() {
List<String> ids = Arrays.asList("205", "10", "308", "49", "627", "193", "111", "193");
String joinResult = ids.stream().collect(Collectors.joining(","));
System.out.println("拼接后:" + joinResult);
}
/**
* 数学运算
*/
@Test
public void testNumberCalculate() {
List<Integer> ids = Arrays.asList(10, 20, 30, 40, 50);
// 计算平均值
Double average = ids.stream().collect(Collectors.averagingInt(value -> value));
System.out.println("平均值:" + average);
// 数据统计信息
IntSummaryStatistics summary = ids.stream().collect(Collectors.summarizingInt(value -> value));
System.out.println("数据统计信息: " + summary);
}
}
@Data
@AllArgsConstructor
class User {
private int id;
}
Loading…
Cancel
Save