JAVA 用ArrayList對對象中某屬性排序

 

一段樣本程式：

對Student類中的年齡按從小到大排序

import java.io.*;<br />import java.math.*;<br />import java.util.*;<br />import java.text.*;</p><p>class Student{<br /> int age;<br /> int id;<br /> String gender;<br /> String name;<br /> String cs;<br /> Student(int id,String name,String gender,int age,String cs){<br /> this.age=age;<br /> this.name=name;<br /> this.gender=gender;<br /> this.id=id;<br /> this.cs=cs;<br /> }<br /> public String toString(){<br /> return id+" "+name+" "+gender+" "+age+" "+cs;<br /> }<br />}<br />public class Main {<br /> public static void main(String[] args) {<br /> Comparator<Student> comparator = new Comparator<Student>(){<br /> public int compare(Student s1, Student s2) {<br /> //先排年齡<br /> if(s1.age!=s2.age){<br /> return s1.age-s2.age;<br /> }<br /> else{<br /> //年齡相同則按姓名排序<br /> if(!s1.name.equals(s2.name)){<br /> return s1.name.compareTo(s2.name);<br /> }<br /> else{<br /> //姓名也相同則按學號排序<br /> return s1.id-s2.id;<br /> }<br /> }<br /> }<br /> };<br /> Student stu1 = new Student (1,"zhangsan","male",28,"cs");<br /> Student stu2 = new Student (2,"lisi","female",19,"cs");<br /> Student stu3 = new Student (3,"wangwu","male",22,"cs");<br /> Student stu4 = new Student (4,"zhaoliu","female",17,"cs");<br /> Student stu5 = new Student (5,"jiaoming","male",22,"cs");</p><p> ArrayList<Student> List = new ArrayList<Student>();<br /> List.add(stu1);<br /> List.add(stu2);<br /> List.add(stu3);<br /> List.add(stu4);<br /> List.add(stu5);<br /> //這裡就會自動根據規則進行排序<br /> Collections.sort(List,comparator);<br /> display(List);<br /> }<br /> static void display(ArrayList<Student> lst){<br /> for(Student s:lst)<br /> System.out.println(s);<br /> }<br />}