需要引包：
compile group: 'com.google.guava', name: 'guava', version: '28.1-jre'package com.zhuzhuxia.demo; import com.alibaba.fastjson.JSON; import com.alibaba.fastjson.JSONArray; import com.google.common.collect.Lists; import org.junit.jupiter.api.Test; import java.util.Comparator; import java.util.List; import java.util.Map; import java.util.stream.Collectors; /** * @Author: 猪猪侠 * @Date: 2019/10/30 17:59 * @Version: 1.0 * @Description: */ public class MyTest { @Test public void listTest(){ List<Integer> integerList = Lists.newArrayList(1, 2, 3, 4, 5, 6, 3, 5, 1, 4, 2, 8, 9); List<Student> studentList = Lists.newArrayList(); Student stu1 = new Student(1L,"张三",15); Student stu2 = new Student(2L,"李四",11); Student stu3 = new Student(3L,"王五",12); Student stu4 = new Student(4L,"赵六",10); studentList.add(stu1); studentList.add(stu2); studentList.add(stu3); studentList.add(stu4); System.out.println("学生原数据："+JSONArray.toJSON(studentList)); System.out.println("-----------------------------------------------------"); List<Student> collect1 = studentList.stream().filter(stu -> stu.getName().equals("张三")).collect(Collectors.toList()); System.out.println("查出姓名是“张三”的学生："+JSONArray.toJSON(collect1)); List<Integer> collect2 = studentList.stream().map(stu -> stu.getAge()).collect(Collectors.toList()); System.out.println("取出学生的年龄集合："+collect2); List<Integer> collect6 = studentList.stream().map(stu -> stu.getAge()).distinct().collect(Collectors.toList()); System.out.println("取出学生的年龄集合并去重："+collect6); List<Student> collect3 = studentList.stream().skip(3).collect(Collectors.toList()); System.out.println("学生集合里去除前三个："+JSONArray.toJSON(collect3)); List<Student> collect4 = studentList.stream().limit(3).collect(Collectors.toList()); System.out.println("学生集合里取前三个："+JSONArray.toJSON(collect4)); Map<Integer, List<Student>> collect5 = studentList.stream().collect(Collectors.groupingBy(student -> student.getAge())); System.out.println("根据学生年龄分组："+JSONArray.toJSON(collect5)); int ageSum = studentList.stream().mapToInt(stu -> stu.getAge()).sum(); System.out.println("找出学生年龄之和："+ageSum); int ageMax= studentList.stream().mapToInt(stu -> stu.getAge()).max().getAsInt(); System.out.println("找出学生年龄最大："+ageMax); int ageMin= studentList.stream().mapToInt(stu -> stu.getAge()).min().getAsInt(); System.out.println("找出学生年龄最小："+ageMin); Double aggAverage = studentList.stream().mapToInt(stu -> stu.getAge()).average().getAsDouble(); System.out.println("找出学生年龄最小："+aggAverage); studentList.sort((a,b) -> b.getAge().compareTo(a.getAge())); System.out.println("根据学生年龄降序："+JSONArray.toJSON(studentList)); studentList.sort((a,b) -> a.getAge().compareTo(b.getAge())); System.out.println("根据学生年龄升序："+JSONArray.toJSON(studentList)); } public static class Student{ private Long id; private String name; private Integer age; public Student(Long id, String name,Integer age) { this.id = id; this.name = name; this.age = age; } public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } } } 运行结果： 学生原数据：[{"name":"张三","id":1,"age":15},{"name":"李四","id":2,"age":11},{"name":"王五","id":3,"age":12},{"name":"赵六","id":4,"age":10}] ----------------------------------------------------- 查出姓名是“张三”的学生：[{"name":"张三","id":1,"age":15}] 取出学生的年龄集合：[15, 11, 12, 10] 取出学生的年龄集合并去重：[15, 11, 12, 10] 学生集合里去除前三个：[{"name":"赵六","id":4,"age":10}] 学生集合里取前三个：[{"name":"张三","id":1,"age":15},{"name":"李四","id":2,"age":11},{"name":"王五","id":3,"age":12}] 根据学生年龄分组：{"11":[{"name":"李四","id":2,"age":11}],"12":[{"name":"王五","id":3,"age":12}],"15":[{"name":"张三","id":1,"age":15}],"10":[{"name":"赵六","id":4,"age":10}]} 找出学生年龄之和：48 找出学生年龄最大：15 找出学生年龄最小：10 找出学生年龄最小：12.0 根据学生年龄降序：[{"name":"张三","id":1,"age":15},{"name":"王五","id":3,"age":12},{"name":"李四","id":2,"age":11},{"name":"赵六","id":4,"age":10}] 根据学生年龄升序：[{"name":"赵六","id":4,"age":10},{"name":"李四","id":2,"age":11},{"name":"王五","id":3,"age":12},{"name":"张三","id":1,"age":15}]
