java List的排序
List自定义排序
1、第一种方法，就是list中对象实现Comparable接口，重写compareTo接口， 对排序的字段进行比较。
2、第二种方法，就是在重载Collections.sort方法。
代码示例
package com.xmy.list.sort;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
* description:list排序
* Created with IDEA
* User:xmy
* Date:2016/10/14
* Time:10:10
*/
public class ListMain {
public static void main(String[] args) {
comparePersonOrder();
compareStudentOrder();
compareStudentOrder2();
}
/**
* 重载Collections.sort
*/
public static void compareStudentOrder2(){
List<Student> listA = new ArrayList<Student>();
listA.add(new Student("name2", 2));
listA.add(new Student("name1", 1));
listA.add(new Student("name3", 3));
Collections.sort(listA, new Comparator<Student>() {
@Override
public int compare(Student o1, Student o2) {
return o1.getOrder().compareTo(o2.getOrder());
}
});
System.out.println("**********升序**********");
for (Student s : listA) {
System.out.println(s);
}
}
/**
* 重载Collections.sort
*/
public static void compareStudentOrder(){
List<Student> listA = new ArrayList<Student>();
listA.add(new Student("name2", 2));
listA.add(new Student("name1", 1));
listA.add(new Student("name3", 3));
System.out.println("**********升序**********");
//升序
Collections.sort(listA, new SortNum());
for (Student s : listA) {
System.out.println(s);
}
//降序
System.out.println("**********降序**********");
Comparator result = Collections.reverseOrder(new SortNum());
Collections.sort(listA,result);
for (Student s : listA) {
System.out.println(s);
}
}
/**
* Person实现Comparable接口
*/
public static void comparePersonOrder(){
List<Person> listA = new ArrayList<Person>();
listA.add(new Person("name2", 2));
listA.add(new Person("name1", 1));
listA.add(new Person("name3", 3));
//升序
Collections.sort(listA);
System.out.println("**********升序**********");
for (Person p : listA) {
System.out.println(p);
}
//降序
Collections.reverse(listA);
System.out.println("**********降序**********");
for (Person p : listA) {
System.out.println(p);
}
}
}
/**
* 比较器类
*/
class SortNum implements Comparator{
@Override
public int compare(Object o1, Object o2){
Student s1 = (Student)o1;
Student s2 = (Student)o2;
return s1.getOrder() - s2.getOrder();
}
}
class Student {
private String name;
private Integer order;
public Student(String name, Integer order){
this.name = name;
this.order = order;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getOrder() {
return order;
}
public void setOrder(Integer order) {
this.order = order;
}
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", order=" + order +
'}';
}
}
class Person implements Comparable<Person> {
private String name;
private Integer order;
@Override
public String toString() {
return "Person{" +
"order=" + order +
", name='" + name + '\'' +
'}';
}
public Person(String name, Integer order){
this.name = name;
this.order = order;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getOrder() {
return order;
}
public void setOrder(Integer order) {
this.order = order;
}
@Override
public int compareTo(Person arg0) {
return this.getOrder().compareTo(arg0.getOrder());
}
}
对复合数据类型的数据的排序
package com.xmy.list.sort;
import java.util.Arrays;
import java.util.Comparator;
/**
* description:
* Created with IDEA
* User:xmy
* Date:2016/11/14
* Time:15:55
*/
public class ArrayTest {
public static void main(String[] args) {
compareOrder();
}
/**
* 排序
*/
public static void compareOrder(){
Point[] points = new Point[4];
for(int i=0;i<4;i++)
points[i]=new Point();
//初始化数据
points[0].order_1=2;points[0].order_2=1;
points[1].order_1=2;points[1].order_2=2;
points[2].order_1=1;points[2].order_2=2;
points[3].order_1=0;points[3].order_2=1;
//自定义排序
Arrays.sort(points, new MyComprator());
//输出排序结果
for(int i=0;i<4;i++)
System.out.println("排序后("+points[i].order_1+","+points[i].order_2+")");
}
}
class Point{
int order_1;
int order_2;
}
/**
* 比较器类
*/
class MyComprator implements Comparator {
public int compare(Object arg0, Object arg1) {
Point point_1 = (Point)arg0;
Point point_2 = (Point)arg1;
//优先按order_1进行升序排列
if(point_1.order_1 != point_2.order_1)
return point_1.order_1 > point_2.order_1 ? 1:-1;
//再按order_2进行升序排列
else
return point_1.order_2 > point_2.order_2 ? 1:-1;
}
}
List默认排序
/**
* 默认list排序方法
*/
public static void sortList(){
List<String> list = new ArrayList();
list.add("赵");
list.add("钱");
list.add("孙");
list.add("李");
list.add("周");
//注意：是根据的汉字的拼音的字母排序的，而不是根据汉字一般的排序方法
System.out.println("**********升序**********");
Collections.sort(list,Collator.getInstance(Locale.CHINA));
for(String temp : list){
System.out.println(temp);
}
System.out.println("**********降序**********");
Collections.reverse(list);
for(String temp : list){
System.out.println(temp);
}
}
数组的排序
1、int[]，double[]，char[]等基数据类型的数组，Arrays类之只是提供了默认的升序排列
/**
* 默认数组排序方法
*/
public static void sortArray(){
String[] names = {"赵", "钱", "孙", "李", "周"};
System.out.println("排序前：" + Arrays.toString(names));
//Arrays.sort(names); 排序无效
Arrays.sort(names, Collator.getInstance(Locale.SIMPLIFIED_CHINESE));//升序;
System.out.println(" 升序：" + Arrays.toString(names));
Integer[] ages = {5,7,2,8,1};
System.out.println("排序前：" + Arrays.toString(ages));
Arrays.sort(ages);
System.out.println(" 升序：" + Arrays.toString(ages));
}
枚举类型的排序
对于枚举类型的enum1.compareTo（enum2）是按照枚举类型值在定义时的先后顺序比较的，越后面的越大，跟值的字母先后顺序无关。
