对象排序得到方式

        java实现 list 排序的方式，有三种

        ① 对象实现Comparable 接口，然后代码里直接调用Collections.sort(list)

        ②使用内部类Comparator

        ③使用stream.sort

代码如下

        实现Comparable接口的实体类

@Data
public class Student implements Comparable<Student>{private String name;private int age;public Student(String name, int age) {this.name = name;this.age = age;}@Overridepublic int compareTo(Student s1) {return this.age - s1.age;}
}

        没实现Comparable接口的实体类

@Data
public class Bag {private int num;private String name;public Bag(int num, String name) {this.num = num;this.name = name;}
}

        几种排序的方式都在下面了：

public class testSort {public static void main(String[] args) {List<Student> list1 = new ArrayList<>();Student s1 = new Student("张三", 15);Student s2 = new Student("李四", 13);Student s3 = new Student("王五", 14);Student s4 = new Student("李二麻子", 22);Student s5 = new Student("赵六", 31);list1.add(s1);list1.add(s2);list1.add(s3);list1.add(s4);list1.add(s5);Collections.sort(list1);for (Student student : list1) {System.out.println(student.getName() + "----" + student.getAge());}System.out.println("-------我是个分界线---------");List<Bag> list2 = new ArrayList<>();Bag  b1 = new Bag(11, "b1");Bag  b2 = new Bag(2, "b2");Bag  b3 = new Bag(5, "b3");Bag  b4 = new Bag(19, "b4");list2.add(b1);list2.add(b2);list2.add(b3);list2.add(b4);// 可以使用lamda表达式写法Collections.sort(list2 ,(p1, p2) ->{return p1.getNum()-p2.getNum();});/* 可以采取匿名内部类写法Collections.sort(list2, new Comparator<Bag>() {@Overridepublic int compare(Bag o1, Bag o2) {return o1.getNum() - o2.getNum();}});*/for (Bag bag : list2) {System.out.println(bag.getName() + "----" + bag.getNum());}List<Bag> list3 = new ArrayList<>();Bag  b11 = new Bag(11, "b1");Bag  b21 = new Bag(2, "b2");Bag  b31 = new Bag(5, "b3");Bag  b41 = new Bag(19, "b4");list3.add(b11);list3.add(b21);list3.add(b31);list3.add(b41);// 这个stream。sort一定要接受返回值，否则源对象不变list3 = list3.stream().sorted(Comparator.comparing(p -> p.getNum())).collect(Collectors.toList());// 或者直接stream流里直接操作打印啥的//list3.stream().sorted(Comparator.comparing(p -> p.getNum())).forEach(System.out::println);System.out.println("--------我是个分界线--------");for (Bag bag : list3) {System.out.println(bag.getName() + "----" + bag.getNum());}}
}