jdk8- list操作

Posted 2020-09-30 远方的风lyh

本文版权归 远方的风lyh和博客园共有，欢迎转载，但须保留此段声明，并给出原文链接，谢谢合作。

 

student类

public class Student {
    private String age;
    private Integer sex;
     //省略get set。。。
}

Demo类

class Demo{
    private String name;
    private  Integer sex;
    private  String age;

    public Demo(String age,Integer sex) {
        this.age =age;
        this.sex =sex;
    }

 //省略get set。。

 }

list操作

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<Demo>();
        //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<Demo>) demos;
        Comparator<Demo> comparator = (h1, h2) -> h1.getAge().compareTo(h2.getAge());
        demos.sort(comparator.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<String, List<Demo>> demoOder = demos.stream().collect(Collectors.groupingBy(Demo::getAge));
        System.out.println(demoOder);


    }
}

 

 操作效果：