java教程之二个arraylist排序的示例分享

示例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("丁晓宇", 21);
  student dxy = new student("赵四", 22);
  student cjc = new student("张三", 11);
  student lgc = new student("刘武", 19);
  list<student> studentlist = new arraylist<student>();
  studentlist.add(zlj);
  studentlist.add(dxy);
  studentlist.add(cjc);
  studentlist.add(lgc);
  system.out.println("按照年齡排序：");
  collections.sort(studentlist, new sortbyage());
  for (student student : studentlist) {
   system.out.println(student.getname() + " / " + student.getage());
  }
  system.out.println(" ========= ");
  system.out.println("按照姓名排序");
  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;
 }
}

示例2

常常遇到数组排序的问题.比如我有一个person类,它的实例对象存储在arraylist数组中,现在要把arraylist数组中 的person对象按照年龄排序.
其实这种情况经常遇到.
下面给出源代码:

1:person.java文 件:

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

// 实现comparator接口,也就是定义排序规则,你几乎可以定义任何规则
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());
         } 

     }

}

当然，如果你的list包装的是基本类型或者string，则只要 collections.sort(list);即可