java对LIst的排序

public class Student {
    private Integer index;
    private String name;
    private Integer age;

    public Student() {
    }

    public Student(Integer index, String name, Integer age) {
        this.index = index;
        this.name = name;
        this.age = age;
    }

    public Integer getIndex() {
        return index;
    }

    public void setIndex(Integer index) {
        this.index = index;
    }

    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;
    }

}

List<Student> students = new ArrayList<>();
students.add(new Student(1,"z1",25));
students.add(new Student(12,"z2",26));
students.add(new Student(9,"z3",27));
students.add(new Student(4,"z4",28));
students.add(new Student(1,"z5",29));

//java8之前的排序
Collections.sort(students,new ComparatorChain<Student>(){
     public int compare(Student s1, Student s2) {
          return s1.getIndex().compareTo(s2.getIndex());
     }
});
students.forEach(s->{
     System.out.println(s.toString());
});

Student{index=1, name=‘z1‘, age=25}
Student{index=1, name=‘z5‘, age=29}
Student{index=4, name=‘z4‘, age=28}
Student{index=9, name=‘z3‘, age=27}
Student{index=12, name=‘z2‘, age=26

studentList.sort((Student s1,Student s2)->s1.getIndex().compareTo(s2.getIndex()));
studentList.forEach(s -> {
　　　System.out.println(s.toString());
});

Collections.sort(studentList, Comparator.comparing(Student::getIndex));
studentList.forEach(s -> {
    System.out.println(s.toString());
});