Share two examples of arraylist sorting in the Java tutorial

Example 1

package com.yonyou.test;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class Test {
 public static void main(String[] args) {
  Student zlj = new Student(" Xiao-yu ding ", 21);
  Student dxy = new Student(" Zhao four ", 22);
  Student cjc = new Student(" Zhang SAN ", 11);
  Student lgc = new Student(" Washington ", 19);
  List<Student> studentList = new ArrayList<Student>();
  studentList.add(zlj);
  studentList.add(dxy);
  studentList.add(cjc);
  studentList.add(lgc);
  System.out.println(" Sorted by year: ");
  Collections.sort(studentList, new SortByAge());
  for (Student student : studentList) {
   System.out.println(student.getName() + " / " + student.getAge());
  }
  System.out.println(" ========= ");
  System.out.println(" Sort by name ");
  Collections.sort(studentList, new SortByName());
  for (Student student : studentList) {
   System.out.println(student.getName() + " / " + student.getAge());
  }
 }
}
class SortByAge implements Comparator {
 public int compare(Object o1, Object o2) {
  Student s1 = (Student) o1;
  Student s2 = (Student) o2;
  if (s1.getAge() > s2.getAge())
   return 1;
  else if (s1.getAge() == s2.getAge()) {
   return 0;
  }
  return -1;
 }
}
class SortByName implements Comparator {
 public int compare(Object o1, Object o2) {
  Student s1 = (Student) o1;
  Student s2 = (Student) o2;
  if(s1.getName().compareTo(s2.getName()) < 0)
   return -1;
  else if (s1.getName().compareTo(s2.getName()) > 0) {
   return 1;
  }
  return 0;
 }
}
class Student{
 private int age;
 private String name;
 public int getAge() {
  return age;
 }
 public void setAge(int age) {
  this.age = age;
 }
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
 public Student(String name,int age) {
  this.age = age;
  this.name = name;
 }
}

Example 2

For example, I have a Person class whose instance objects are stored in the ArrayList array, and now I want to sort the Person objects in the ArrayList array by age.
This happens all the time.
The source code is given below:

1: Person. Java documents:

public class Person{
     String name;
     int age;
 public Person(String name,int age){
     this.name = name;
     this.age = age;

 }
 public int getAge() {
     return age;
 }
 public void setAge(int age) {
     this.age = age;
 }
 public String getName() {
     return name;
 }
 public void setName(String name) {
     this.name = name;
 }
}

2: Mycomparator. Java

//Implementing the Comparator interface, which defines collation, lets you define almost any rule
package com.infoearth;
import java.util.*;
public class Mycomparator implements Comparator{
    public int compare(Object o1,Object o2) {
        Person p1=(Person)o1;
        Person p2=(Person)o2;  
       if(p1.age<p2.age)
           return 1;
       else
           return 0;
       }
}

3: ListSort. Java

package com.infoearth;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
public class ListSort {
     public static void main(String[] args){
         ArrayList list = new ArrayList();
         list.add(new Person("lcl",28));
         list.add(new Person("fx",23));
         list.add(new Person("wqx",29));
         Comparator comp = new Mycomparator();
         Collections.sort(list,comp);  
         for(int i = 0;i<list.size();i++){
             Person p = (Person)list.get(i);
             System.out.println(p.getName());
         }  

     }
}

Of course, if your List wraps a base type or String, just collections.sort (List); Can