先简答贴下POM
<?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>2.1.7.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.example.DemoCrud</groupId> <artifactId>democurd</artifactId> <version>0.0.1-SNAPSHOT</version> <name>democurd</name> <description>Demo project for Spring Boot</description> <properties> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-jdbc</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <optional>true</optional> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <!-- mybatis整合Springboot --> <dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> <version>2.1.0</version> </dependency> <dependency> <!-- maven 添加json--> <groupId>net.sf.json-lib</groupId> <artifactId>json-lib</artifactId> <version>2.4</version> </dependency> <!-- 引入org.json所需依赖 --> <dependency> <groupId>com.alibaba</groupId> <artifactId>fastjson</artifactId> <version>1.2.70</version> </dependency> <dependency> <groupId>org.webjars</groupId> <artifactId>jquery</artifactId> <version>3.3.0</version> </dependency> <!--bootstrap-webjar--> <dependency> <groupId>org.webjars</groupId> <artifactId>bootstrap</artifactId> <version>4.0.0</version> </dependency> <!--配置文件注入时使用后会有提示--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-configuration-processor</artifactId> <optional>true</optional> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.18</version> </dependency> <dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.3.1</version> </dependency> <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok --> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.18.12</version> <scope>provided</scope> </dependency> <!-- https://mvnrepository.com/artifact/oracle/oracle-jdbc --> <dependency> <groupId>com.oracle.ojdbc</groupId> <artifactId>ojdbc8</artifactId> <version>19.3.0.0</version> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>fastjson</artifactId> <version>1.2.47</version> </dependency> <!-- Druid 数据源依赖，集成了 Spring boot ，方便配置 druid 属性 --> <!-- https://mvnrepository.com/artifact/com.alibaba/druid-spring-boot-starter --> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid-spring-boot-starter</artifactId> <version>1.2.8</version> </dependency> <!-- Mysql 数据库驱动，spring boot 2.1.3 时，mysql 驱动版本为 8.0.15 --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </dependency> <!-- 引入 Spring Data JPA，JPA 组件内部会依赖 JDBC 组件，JDBC 组件内部默认依赖的是 HikariCP 数据源--> <!--切换 druid 数据源时，HikariCP 依赖可以移除掉，不移除时也不影响--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <!--引用 log4j2 spring boot 启动器，内部依赖了 slf4j、log4j；排除项目中的 logback--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-log4j2</artifactId> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <configuration> <excludes> <exclude> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> </exclude> </excludes> </configuration> </plugin> </plugins> </build> </project>
公共实体类
@Data @Builder public class Student { private Integer age; private String name; private Boolean sex; //true:男 false：女 }
单层循环数据存取List，Map
package com.example.democrud.democurd.Prototype.demo01; import lombok.Builder; import lombok.Data; import org.thymeleaf.expression.Lists; import java.util.*; import java.util.stream.Collectors; public class ListAndMapDemo { public static void main(String[] args) { List<Student> list = stduentInit(); //取出年龄大于等于20岁的 getAge20(list); //拼接字符串 马丹1,马丹2,马丹3,马丹4,马丹5 // getStringName(list); //拼接字符串取年龄 10,15,20,25,30 // getAge(list); //根据年龄分组 10,10,20,20, .... //ageLimi(list); } /** * 根据年龄分组 10,10,20,20, .... * * @param list */ public static void ageLimi(List<Student> list) { //根据年龄分组 Map<String, List<Student>> map = new HashMap<>(); for (Student student : list) { List<Student> students = map.get(student.getAge().toString()); if (students == null) { students = new ArrayList<>(); } students.add(student); map.put(student.getAge().toString(), students); } System.out.println("优化前：" + map); Map<Integer, List<Student>> collect = list.stream().collect(Collectors.groupingBy(Student::getAge)); System.out.println("优化前：" + collect); } /** * 拼接字符串取年龄 10,15,20,25,30 * * @param list */ public static void getAge(List<Student> list) { // 无法处理空 // String collect = list.stream().map(v -> v.getAge().toString()).collect(Collectors.joining(",")); // System.out.println("无法处理空"+collect); String collect1 = list.stream().filter(v -> v.getAge() != null).map(Student::getAge).map(String::valueOf).collect(Collectors.joining(",")); System.out.println("可以处理优化前" + collect1); String collect2 = list.stream().filter(v -> !Objects.isNull(v.getAge())).map(Student::getAge).map(String::valueOf).collect(Collectors.joining(",")); System.out.println("可以处理优化后" + collect2); } /** * 拼接字符串 马丹1,马丹2,马丹3,马丹4,马丹5 * * @param list */ public static void getStringName(List<Student> list) { StringBuffer buffer = new StringBuffer(); for (Student student : list) { buffer.append(student.getName()); buffer.append(","); } String substring = buffer.toString().substring(0, buffer.toString().length() - 1); System.out.println("优化前：" + substring); String collect = list.stream().map(v -> v.getName()).collect(Collectors.joining(",")); System.out.println("优化后：" + collect); } /** * 取出年龄大于等于20岁的 */ public static void getAge20(List<Student> list) { //实现一 int ages = 20; List<Student> list1 = new ArrayList<Student>(); for (Student student5 : list) { if (student5.getAge() >= ages) { list1.add(student5); } } System.out.println("优化前：" + list1); //实现二 list = list.stream().filter(v -> v.getAge() >= 20).collect(Collectors.toList()); System.out.println("优化后：" + list); } /** * 初始化list对象 */ public static List<Student> stduentInit() { List<Student> list = new ArrayList<Student>(); // Student student = new Student(null, "马丹1", true); Student student = new Student(10, "马丹1", true); Student student1 = new Student(20, "马丹2", false); Student student2 = new Student(10, "马丹3", true); Student student3 = new Student(10, "马丹4", false); Student student4 = new Student(20, "马丹5", true); list.add(student); list.add(student1); list.add(student2); list.add(student3); list.add(student4); return list; } }
运行效果一一进行展示：
1.取出年龄大于等于20岁的
//取出年龄大于等于20岁的 getAge20(list);
List原始数据==>[Student(age=10, name=马丹1, sex=true), Student(age=20, name=马丹2, sex=false), Student(age=10, name=马丹3, sex=true), Student(age=10, name=马丹4, sex=false), Student(age=20, name=马丹5, sex=true)] 优化前：[Student(age=20, name=马丹2, sex=false), Student(age=20, name=马丹5, sex=true)] 优化后：[Student(age=20, name=马丹2, sex=false), Student(age=20, name=马丹5, sex=true)]
2.拼接字符串 马丹1,马丹2…
//拼接字符串 马丹1,马丹2,马丹3,马丹4,马丹5 getStringName(list);
List原始数据==>[Student(age=10, name=马丹1, sex=true), Student(age=20, name=马丹2, sex=false), Student(age=10, name=马丹3, sex=true), Student(age=10, name=马丹4, sex=false), Student(age=20, name=马丹5, sex=true)] 优化前：马丹1,马丹2,马丹3,马丹4,马丹5 优化后：马丹1,马丹2,马丹3,马丹4,马丹5
3. 拼接字符串取年龄 10,15,20,25,30
//拼接字符串取年龄 10,15,20,25,30 getAge(list);
List原始数据==>[Student(age=10, name=马丹1, sex=true), Student(age=20, name=马丹2, sex=false), Student(age=10, name=马丹3, sex=true), Student(age=10, name=马丹4, sex=false), Student(age=20, name=马丹5, sex=true)] 可以处理优化前10,20,10,10,20 可以处理优化后10,20,10,10,20
4.0根据年龄分组 10,10,20,20, …
//根据年龄分组 10,10,20,20, .... ageLimi(list);
List原始数据==>[Student(age=10, name=马丹1, sex=true), Student(age=20, name=马丹2, sex=false), Student(age=10, name=马丹3, sex=true), Student(age=10, name=马丹4, sex=false), Student(age=20, name=马丹5, sex=true)] 可以处理优化前10,20,10,10,20 可以处理优化后10,20,10,10,20
多层循环嵌套
package com.example.democrud.democurd.Prototype.demo01; import com.alibaba.fastjson.JSON; import com.alibaba.fastjson.JSONArray; import com.alibaba.fastjson.JSONObject; import java.util.*; import java.util.stream.Collectors; public class ListAndMap1Demo { public static void main(String[] args) { // 循环中获取数据 // stduentgetName(); //处理异常嵌套数据 stduents(); } public static void stduentgetName() { Map<String, List<Student>> map = stduentInit(); //System.out.println(JSONObject.toJSON(map)); for (Map.Entry<String, List<Student>> entry : map.entrySet()) { String key = entry.getKey(); List<Student> list = entry.getValue(); System.out.println("key===>"+key); System.out.println("list===>"+list); List<String> collect = list.stream().map(Student::getName).collect(Collectors.toList()); System.out.println("list： 集合数组==》" + collect); String collect1 = list.stream().map(Student::getName).collect(Collectors.joining(",")); System.out.println("string： String数组==》" + collect1); System.out.println("--------------------------------------1---------------------------------------------"); List<Student> collectle = list.stream().filter(v -> v.getAge() >= 20).collect(Collectors.toList()); System.out.println("collectle==>"+collectle); System.out.println("---------------------------------2--------------------------------------------------"); List<String> strList = new ArrayList<>(); for (Student stu : list) { strList.add(stu.getName()); } System.out.println("strList: " + strList); } } /** * 处理深层嵌套异常数据 */ public static void stduents() { List<Map<String, String>> list = new ArrayList<>(); String str = "{\"sheets\":[{\"datas\":[{\"cells\":[{\"dataType\":2,\"value\":\"闫文超\"},{\"dataType\":1,\"value\":\"10.0\"}]},{\"cells\":[{\"dataType\":2,\"value\":\"老王\"},{\"dataType\":1,\"value\":\"20.0\"}]}],\"name\":\"Sheet1\",\"titles\":[\"Name\",\"AGE\"]}]}"; JSONObject js = JSONObject.parseObject(str); //System.out.println(js); String sheets = js.get("sheets").toString(); //System.out.println(sheets); JSONArray objects = JSONArray.parseArray(sheets); //System.out.println(objects); for (Object object : objects) { JSONObject js111 = JSONObject.parseObject(object.toString()); //System.out.println(js111); String datas = js111.get("datas").toString(); //System.out.println(datas); JSONArray objects1 = JSONArray.parseArray(datas); //System.out.println(objects1); for (Object o : objects1) { JSONObject js1111 = JSONObject.parseObject(o.toString()); //System.out.println(js1111); String cells = js1111.get("cells").toString(); //System.out.println(cells); JSONArray objects2 = JSONArray.parseArray(cells); //System.out.println("objects2 : "+ objects2); for (Object o1 : objects2) { JSONObject js11111 = JSONObject.parseObject(o1.toString()); //System.out.println(js11111); String dataType = js11111.get("dataType").toString(); String value = js11111.get("value").toString(); Map<String, String> map = new HashMap<>(); map.put(dataType, value); list.add(map); //System.out.println("这他妈那个傻逼写的 dataType=" + dataType + " value="+ value); } } } System.out.println(list); } /** * 初始化list对象 */ public static Map<String, List<Student>> stduentInit() { Map<String, List<Student>> map = new HashMap<>(); List<Student> list = new ArrayList<>(); Student student = new Student(10, "马丹1", true); Student student1 = new Student(15, "马丹2", false); Student student2 = new Student(20, "马丹3", true); Student student3 = new Student(25, "马丹4", false); Student student4 = new Student(30, "马丹5", true); list.add(student); list.add(student1); list.add(student2); list.add(student3); list.add(student4); map.put("list", list); List<Student> list1 = new ArrayList<>(); Student stu = new Student(10, "马丹1", true); Student stu1 = new Student(15, "马丹2", false); Student stu2 = new Student(20, "马丹3", true); Student stu3 = new Student(25, "马丹4", false); Student stu4 = new Student(30, "马丹5", true); list1.add(stu); list1.add(stu1); list1.add(stu2); list1.add(stu3); list1.add(stu4); map.put("list1", list1); return map; } }
1.处理异常嵌套数据
//处理异常嵌套数据 stduents();
此处不理解的可以把sout注释取下；每步都有打印我这边为了更好的展示就先注释了；
[{2=闫文超}, {1=10.0}, {2=老王}, {1=20.0}]
2.循环中获取数据
// 循环中获取数据 stduentgetName();
key===>list1 list===>[Student(age=10, name=马丹1, sex=true), Student(age=15, name=马丹2, sex=false), Student(age=20, name=马丹3, sex=true), Student(age=25, name=马丹4, sex=false), Student(age=30, name=马丹5, sex=true)] list： 集合数组==》[马丹1, 马丹2, 马丹3, 马丹4, 马丹5] string： String数组==》马丹1,马丹2,马丹3,马丹4,马丹5 --------------------------------------1--------------------------------------------- collectle==>[Student(age=20, name=马丹3, sex=true), Student(age=25, name=马丹4, sex=false), Student(age=30, name=马丹5, sex=true)] ---------------------------------2-------------------------------------------------- strList: [马丹1, 马丹2, 马丹3, 马丹4, 马丹5] key===>list list===>[Student(age=10, name=马丹1, sex=true), Student(age=15, name=马丹2, sex=false), Student(age=20, name=马丹3, sex=true), Student(age=25, name=马丹4, sex=false), Student(age=30, name=马丹5, sex=true)] list： 集合数组==》[马丹1, 马丹2, 马丹3, 马丹4, 马丹5] string： String数组==》马丹1,马丹2,马丹3,马丹4,马丹5 --------------------------------------1--------------------------------------------- collectle==>[Student(age=20, name=马丹3, sex=true), Student(age=25, name=马丹4, sex=false), Student(age=30, name=马丹5, sex=true)] ---------------------------------2-------------------------------------------------- strList: [马丹1, 马丹2, 马丹3, 马丹4, 马丹5]
欧克；演示完成后续有其他部分会补充；此处感谢吊毛同学的交流；
