Arraylist的sort方法使用

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package com.mac.test;import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.List;public class ArraylistSort {    public static void main(String[] args) {        List<Student> list = new ArrayList<Student>();        Student s1 = new Student();        Student s2 = new Student();        Student s3 = new Student();        Student s4 = new Student();        s1.setId(1);        s1.setName("s1");        s2.setId(2);        s2.setName("s2");        s3.setId(3);        s3.setName("s3");        s4.setId(4);        s4.setName("s4");        list.add(s2);        list.add(s1);        list.add(s4);        list.add(s3);        for (Student student : list) {            System.out.println(student.getId());        }        System.out.println("-----------------");        SortById sb = new SortById();        Collections.sort(list, sb);        for (Student student : list) {            System.out.println(student.getId());        }    }}class SortById implements Comparator<Object> {    @Override    public int compare(Object o1, Object o2) {        Student s1 = (Student) o1;        Student s2 = (Student) o2;        if (s1.getId() < s2.getId()) {            return 1;        } else if (s1.getId() == s2.getId()) {            return 0;        }         return -1;    }}class Student{    private int id;    private String name;    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}
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