首页 > 代码库 > Java中Collections类的排序sort函数两种用法 (转http://viver120.blog.163.com/blog/static/60072482013010111228695/)
Java中Collections类的排序sort函数两种用法 (转http://viver120.blog.163.com/blog/static/60072482013010111228695/)
java中的Colletions类主要实现列表List的排序功能。根据函数参数的传递,具体的排序可以分为 :
1. 自然排序(natural ordering)。
函数原型:sort(List<T> list)
说明:参数是要参与排序列表的List对象
实例说明:参与排序的列表的元素Student必须实现Comparable接口的
public int compareTo(Object o) 方法,在里面写对比的原则。
然后调用Colletions.sort(排序对象的列表)
请看如下示例:
import java.util.ArrayList;import java.util.Arrays;import java.util.Collection;import java.util.Collections;import java.util.Iterator;import java.util.List;class ArrayListTest{public static void printElements(Collection c){ Iterator it = c.iterator(); while(it.hasNext()){ System.out.println(it.next());}}public static void main(String[] args){ ArrayList<Student> al = new ArrayList<Student>(); al.add(new Student(2,"aora")); al.add(new Student(1,"longyu")); al.add(new Student(3,"goso")); Collections.sort(al); printElements(al);}}class Student implements Comparable{ int num; String name; Student(int num,String name){ this.num = num; this.name = name;} public int compareTo(Object o) { Student s = (Student)o; return num > s.num ? 1 : (num == s.num ? 0 : -1); }; public String toString(){ return "num = " + this.num + ",name = " + this.name; } }
2. 实现比较器(Comparator)接口。
函数原型:sort(List<T> list, Comparator<? super T> c)
说明:第一个参数同左,第二个参数是构建对比规则的对比器Comparator。
实例说明(如下):在参与排序的列表的元素Student中写一个内部类作为
Student的对比器,这个对比器要实现Comparator接口的public int compare(Object o1,
Object o2)方法,然后调用Colletions.sort(排序对象的列表,对比器)
请看如下示例:
1 import java.util.ArrayList; 2 import java.util.Collection; 3 import java.util.Collections; 4 import java.util.Iterator; 5 import java.util.Comparator;
6 class ArrayListTest{ 7 public static void printElements(Collection c){ 8 Iterator it = c.iterator(); 9 while(it.hasNext()){10 System.out.println(it.next());11 }12 }
13 public static void main(String[] args){14 ArrayList<Student> al = new ArrayList<Student>();15 al.add(new Student(2,"qingan"));16 al.add(new Student(1,"longyu"));17 al.add(new Student(3,"goso"));18 al.add(new Student(2,"aora"));19 Collections.sort(al,new Student.studentComparator());20 printElements(al);21 }22 }
23 class Student{24 int num;25 String name;26 Student(int num,String name){27 this.num = num;28 this.name = name;29 }30 static class studentComparator implements Comparator{31 public int compare(Object o1,Object o2){32 Student s1 = (Student)o1;33 Student s2 = (Student)o2;34 int result = s1.num > s2.num ? 1 : (s1.num == s2.num ? 0 : -1);35 // 注意:此处在对比num相同时,再按照name的首字母比较。36 if(result == 0){37 result = s1.name.compareTo(s2.name);38 }39 return result;40 } 41 } 42 public String toString(){43 return "num = " + this.num + ",name = " + this.name;44 } 45 }
Java中Collections类的排序sort函数两种用法 (转http://viver120.blog.163.com/blog/static/60072482013010111228695/)
声明:以上内容来自用户投稿及互联网公开渠道收集整理发布,本网站不拥有所有权,未作人工编辑处理,也不承担相关法律责任,若内容有误或涉及侵权可进行投诉: 投诉/举报 工作人员会在5个工作日内联系你,一经查实,本站将立刻删除涉嫌侵权内容。