初始化

.gitignore

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+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store

.idea/.gitignore

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+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml

.idea/encodings.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="Encoding">
+    <file url="file://$PROJECT_DIR$/src/main/java" charset="UTF-8" />
+    <file url="file://$PROJECT_DIR$/src/main/resources" charset="UTF-8" />
+  </component>
+</project>

.idea/misc.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ExternalStorageConfigurationManager" enabled="true" />
+  <component name="MavenProjectsManager">
+    <option name="originalFiles">
+      <list>
+        <option value="$PROJECT_DIR$/pom.xml" />
+      </list>
+    </option>
+  </component>
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" default="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

.idea/vcs.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>

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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.icecream</groupId>
+    <artifactId>zgl-rikao-day19-8-8</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>

src/main/java/com/muyu/pojo/Student.java

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+package com.muyu.pojo;
+
+
+
+
+public class Student {
+    /**
+     * 编号
+     */
+    private int id;
+    /**
+     * 姓名
+     */
+    private String name;
+    /**
+     * 科目
+     */
+    private String subject;
+    /**
+     * 分数
+     */
+    private int score;
+
+    @Override
+    public String toString() {
+        return
+                "编号:" + id +
+                "姓名:" + name +
+                "科目:" + subject +
+                "分数" + score ;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getSubject() {
+        return subject;
+    }
+
+    public void setSubject(String subject) {
+        this.subject = subject;
+    }
+
+    public int getScore() {
+        return score;
+    }
+
+    public void setScore(int score) {
+        this.score = score;
+    }
+
+    public Student() {
+    }
+
+    public Student(int id, String name, String subject, int score) {
+        this.id = id;
+        this.name = name;
+        this.subject = subject;
+        this.score = score;
+    }
+}

src/main/java/com/muyu/test/StudentTest.java

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+package com.muyu.test;
+
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public class StudentTest {
+    public static void main(String[] args) {
+        List<String> studentInfoStrings = new ArrayList<>();
+        //创建并添加学生信息到集合
+        studentInfoStrings.add("1,张三,语文,100");
+        studentInfoStrings.add("1,张三,数学,90");
+        studentInfoStrings.add("2,李四,语文,95");
+        studentInfoStrings.add("2,李四,数学,92");
+        studentInfoStrings.add("3,王五,语文,88");
+        studentInfoStrings.add("3,王五,数学,82");
+
+        // 打印集合
+         studentInfoStrings.forEach(System.out::println);
+
+        System.out.println("----------------------添加数据之后-----------------------");
+
+        Map<String, Double> averageScores = studentInfoStrings.stream()
+                .map(s -> s.split(","))
+                .collect(Collectors.groupingBy(
+                        arr -> arr[1],  // 假设arr[1]是名字
+                        Collectors.mapping(
+                                arr -> Integer.parseInt(arr[3]),  // 假设arr[3]是分数
+                                Collectors.averagingInt(i -> i)
+                        )
+                ));
+
+        // 输出平均成绩结果
+        averageScores.forEach((name, avgScore) -> System.out.println(name + "的平均成绩是: " + avgScore));
+
+    }
+
+
+}