JDK8对List的简化操作-Lambda表达式

import java.util.*;
import java.util.stream.Collectors;

public class Test {
public static void main(String[] args) {
List 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 demos = new ArrayList();

    // 原始数据
    System.out.println("原始数据 组装list*******************");
    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 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 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 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 demoArray = (ArrayList) demos;
    
    Comparator 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;
}

}