ArrayList集合存储学生对象并按年级排序，若年龄相同，则按姓名首字母排序

public class StudentDemo {
    public static void main(String[] args) {
        ArrayList<Students> arrayList = new ArrayList<>();
        arrayList.add(new Students("张三",14));
        arrayList.add(new Students("李四",12));
        arrayList.add(new Students("王五",16));
        arrayList.add(new Students("哎六",16));
      for (Students s:arrayList){
          System.out.println(s.getName()+s.getAge());

      }


    }
}

public class Students  implements Comparable<Students>{
    private String name;
    private int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Students() {
    }

    public Students(String name, int age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public int compareTo(Students s) {
        int num=this.getAge()-s.getAge();//按照年龄升序排序
        int num1=num==0?this.name.compareTo(s.name):num;//若年龄相同时，按照名字首字母排序
        return num1;
    }
}