示例1
复制代码代码如下:
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:
复制代码代码如下:
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
复制代码代码如下:
// 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
复制代码代码如下:
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