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()); }
如果是Object
则
Arrays.sort(array, Collections.reverseOrder());
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());
}
}}
public int compare(Object o1,Object o2) {
Person p1=(Person)o1;
Person p2=(Person)o2; return p1.age - p2.age;//应该是指age越大越前吧,否则就反过来 p2.age - p1.age// if(p1.age<p2.age) p1 在 p2 前面 返回 < 0
// return 1;
// else //只有相等才可以返回0!,如果 p1 > p2 返回 > 0
// return 0;
}}