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10个必须掌握的lambda表达式

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马府强 2 years ago
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a2ba083572
  1. 33
      lambdatest/.gitignore
  2. 11
      lambdatest/README.md
  3. 68
      lambdatest/pom.xml
  4. 13
      lambdatest/src/main/java/com/example/demo/DemoRequestScopeApplication.java
  5. 167
      lambdatest/src/main/java/com/example/demo/service/TestMain.java
  6. 1
      lambdatest/src/main/resources/application.properties
  7. 21
      lambdatest/src/main/resources/application.yml

33
lambdatest/.gitignore

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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
lambdatest/README.md

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# 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。

68
lambdatest/pom.xml

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<?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>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

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

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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);
}
}

167
lambdatest/src/main/java/com/example/demo/service/TestMain.java

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package com.example.demo.service;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
//简化你的代码,提高生产力:这10个Lambda表达式必须掌握
public class TestMain {
public static void main(String[] args) {
// 1. 使用Lambda表达式进行集合遍历
// List<String> list = Arrays.asList("apple", "banana", "orange");
// for (String fruit : list) {
// System.out.println(fruit);
// }
//
// List<String> list2 = Arrays.asList("apple", "banana", "orange");
// list2.forEach(fruit -> System.out.println(fruit));
// 2. 使用Lambda表达式进行排序
// List<String> list2 = Arrays.asList("apple", "banana", "orange");
// Collections.sort(list2, new Comparator<String>() {
// public int compare(String s1, String s2) {
// return s1.compareTo(s2);
// }
// });
//
// List<String> list = Arrays.asList("apple", "banana", "orange");
// Collections.sort(list, (s1, s2) -> s1.compareTo(s2));
// 3. 使用Lambda表达式进行过滤
// List<String> list = Arrays.asList("apple", "banana", "orange");
// List<String> filteredList = new ArrayList<String>();
// for (String fruit : list) {
// if (fruit.startsWith("a")) {
// filteredList.add(fruit);
// }
// }
//
// List<String> list2 = Arrays.asList("apple", "banana", "orange");
// List<String> filteredLists = list2.
// stream().
// filter(fruit -> fruit.startsWith("a")).
// collect(Collectors.toList());
// 4. 使用Lambda表达式进行映射
// List<String> list = Arrays.asList("apple", "banana", "orange");
// List<Integer> lengths = new ArrayList<Integer>();
// for (String fruit : list) {
// lengths.add(fruit.length());
// }
//
// List<String> lists = Arrays.asList("apple", "banana", "orange");
// List<Integer> lengthss = lists.stream().map(fruit -> fruit.length())
// .collect(Collectors.toList());
// 5. 使用Lambda表达式进行归约
// List<Integer> list = Arrays.asList(1, 2, 3, 4, 5);
// int sum = 0;
// for (int i : list) {
// sum += i;
// }
//
// List<Integer> list2 = Arrays.asList(1, 2, 3, 4, 5);
// int sum2 = list2.stream().reduce(0, (a, b) -> a + b);
// 6. 使用Lambda表达式进行分组
// List<String> list = Arrays.asList("apple", "banana", "orange");
// Map<Integer, List<String>> grouped = new HashMap<Integer, List<String>>();
// for (String fruit : list) {
// int length = fruit.length();
// if (!grouped.containsKey(length)) {
// grouped.put(length, new ArrayList<String>());
// }
// grouped.get(length).add(fruit);
// }
//
//
// List<String> lists = Arrays.asList("apple", "banana", "orange");
// Map<Integer, List<String>> groupeds = lists.stream().collect(Collectors.groupingBy(fruit -> fruit.length()));
// 7. 使用Lambda表达式进行函数式接口的实现
// MyInterface myObject = new MyInterface() {
// public void doSomething(String input) {
// System.out.println(input);
// }
// };
// myObject.doSomething("Hello World");
//
// MyInterface myObject = input -> System.out.println(input);
// myObject.doSomething("Hello World");
//8. 使用Lambda表达式进行线程的创建
// Thread thread = new Thread(new Runnable() {
// public void run() {
// System.out.println("Thread is running.");
// }
// });
// thread.start();
//
// Thread threads = new Thread(() -> System.out.println("Thread is running."));
// threads.start();
// 9. 使用Lambda表达式进行Optional的操作
// String str = "Hello World";
// if (str != null) {
// System.out.println(str.toUpperCase());
// }
//
// Optional<String> strs = Optional.ofNullable("Hello World");
// strs.map(String::toUpperCase).ifPresent(System.out::println);
// 10. 使用Lambda表达式进行Stream的流水线操作
List<String> list = Arrays.asList("apple", "banana", "orange");
List<String> filteredList = new ArrayList<String>();
for (String fruit : list) {
if (fruit.startsWith("a")) {
filteredList.add(fruit.toUpperCase());
}
}
Collections.sort(filteredList);
List<String> lists = Arrays.asList("apple", "banana", "orange");
List<String> filteredLists = lists.stream().filter(fruit -> fruit.startsWith("a")).map(String::toUpperCase).sorted().collect(Collectors.toList());
}
}

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

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

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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
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