1. 跟据某个属性分组OfficeId:
Map<String, List<IncomeSumPojo>> collect = list.stream().collect(Collectors.groupingBy(IncomeSumPojo::getOfficeId));
2. 根据某个属性分组OfficeId,汇总某个属性Money:
Map<String, Double> collect = list.stream().collect(Collectors.groupingBy(IncomeSumPojo::getOfficeId,Collectors.summingDouble(IncomeSumPojo::getMoney)));
3. 根据某个属性添加条件过滤数据:
list = list.stream().filter(u -> !u.getAmount().equals("0.00")).collect(Collectors.toList());
4. 判断一组对象里面有没有属性值是某个值:
List<Menu> menuList = UserUtils.getMenuList();
boolean add = menuList.stream().anyMatch(m -> "plan:ctPlan:add".equals(m.getPermission()));
5. 取出一组对象的某个属性组成一个新集合:
List<String> tableNames=list.stream().map(User::getMessage).collect(Collectors.toList());
6. list去重复:
list = list.stream().distinct().collect(Collectors.toList());
实例如下:
package com.security.common.elk; import java.util.ArrayList; import java.util.Comparator; import java.util.List; import java.util.Map; import java.util.stream.Collectors; public class TEST { public static void main(String[] args) { List<Student> list = new ArrayList<>(); Student student1 = new Student(); student1.setAge("12"); student1.setSex(0); Student student2 = new Student(); student2.setAge("13"); student2.setSex(2); Student student3 = new Student(); student3.setAge("11"); student3.setSex(1); Student student4 = new Student(); student4.setAge("18"); student4.setSex(1); Student student5 = new Student(); student5.setAge("18"); student5.setSex(0); Student student6 = new Student(); student6.setAge("18"); student6.setSex(2); Student student7 = new Student(); student7.setAge("18"); student7.setSex(2); list.add(student1); list.add(student2); list.add(student3); list.add(student4); list.add(student5); list.add(student6); list.add(student7); List<Demo> demos = new ArrayList(); // 原始数据 System.out.println("原始数据 组装list<demo>*******************"); demos = list.stream().map(student -> new Demo(student.getAge(), student.getSex())).collect(Collectors.toList()); demos.forEach(demo -> { System.out.println("年龄 " + demo.getAge() + " 性别 " + demo.getSex() + ","); }); // 只取sex为0 System.out.println("只取sex为0****************"); List<Demo> demorm = demos.stream().filter(demo -> demo.getSex() == 0).distinct().collect(Collectors.toList()); demorm.forEach(demo -> { System.out.println("年龄 " + demo.getAge() + " 性别 " + demo.getSex() + ","); }); // 筛选年龄大于12岁 System.out.println("筛选年龄大于12岁的*************"); List<Demo> demoFilter = demos.stream().filter(demo -> Integer.valueOf(demo.getAge()) > 12).collect(Collectors.toList()); demoFilter.forEach(demo -> { System.out.println("年龄 " + demo.getAge() + " 性别 " + demo.getSex() + ","); }); // 排序 System.out.println("排序******************"); List<Demo> demoSort = demos.stream().sorted((s1, s2) -> s1.getAge().compareTo(s2.getAge())).collect(Collectors.toList()); demoSort.forEach(demo -> { System.out.println("年龄 " + demo.getAge() + " 性别 " + demo.getSex() + ","); }); // 倒序 System.out.println("倒序****************"); ArrayList<Demo> demoArray = (ArrayList) demos; Comparator<Demo> comparator = (h1, h2) -> h1.getAge().compareTo(h2.getAge()); demos.sort(comparator.reversed()); //or demos.sort(Comparator.comparing(Demo::getAge).reversed()); demos.forEach(demo -> { System.out.println("年龄 " + demo.getAge() + " 性别 " + demo.getSex() + ","); }); // 多条件正序 System.out.println("多条件排序正序****************"); demoArray.sort(Comparator.comparing(Demo::getSex).thenComparing(Demo::getAge)); demoArray.forEach(demo -> { System.out.println("年龄 " + demo.getAge() + " 性别 " + demo.getSex() + ","); }); // 多条件倒序 System.out.println("多条件排序倒序 sex 倒序****************"); demoArray.sort(Comparator.comparing(Demo::getSex).reversed().thenComparing(Demo::getAge)); demoArray.forEach(demo -> { System.out.println("年龄 " + demo.getAge() + " 性别 " + demo.getSex() + ","); }); // 按照年龄分组 System.out.println("根据age分组结果为Map****************"); Map demoOder = demos.stream().collect(Collectors.groupingBy(Demo::getAge)); System.out.println(demoOder); } } class Demo { private String name; private Integer sex; private String age; public Demo(String age, Integer sex) { this.age = age; this.sex = sex; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getSex() { return sex; } public void setSex(Integer sex) { this.sex = sex; } public String getAge() { return age; } public void setAge(String age) { this.age = age; } } class Student { private String age; private Integer sex; public String getAge() { return age; } public void setAge(String age) { this.age = age; } public Integer getSex() { return sex; } public void setSex(Integer sex) { this.sex = sex; } }
原文:https://www.cnblogs.com/yuarvin/p/13529675.html