版權聲明:本文爲博主原創文章,未經博主允許不得轉載。 https://blog.csdn.net/Eileen_crystal/article/details/77854866
Java List 按某字段排序
代碼支持:字符串(String)、日期(Date)、整型(Integer)、整形(Long)
MODEl
package com.eileen.feng.dto.stat;
/**
* Created by Xuefeng_Wen on 2017/9/5.
*/
public class StatChargingDto{
/** 省市code */
private java.lang.String code;
/** 行政區劃名稱*/
private java.lang.String name;
/** 數量*/
private Long chargingStationCount;
// END
public StatChargingDto() {
}
public StatChargingDto(String code, String name, Long chargingStationCount) {
this.code = code;
this.name = name;
this.chargingStationCount = chargingStationCount;
}
public String getCode() {
return code;
}
public void setCode(String code) {
this.code = code;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Long getChargingStationCount() {
return chargingStationCount;
}
public void setChargingStationCount(Long chargingStationCount) {
this.chargingStationCount = chargingStationCount;
}
}
UTIL
package com.eileen.feng.util;
import com.eileen.feng.dto.stat.StatChargingDto;
import java.util.*;
import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;
/**
* 這是一個自定義排序的類,專門針對列表(List)中的數據進行排序;可按指定方法進行。
* 目前實現對字符串(String)、日期(Date)、整型(Integer)、整形(Long) 等四種對象進行排序。
* @author Xuefeng_Wen
*
* @param <E>
*/
public class MySortList<E> {
/**
* 對列表中的數據按指定字段進行排序。要求類必須有相關的方法返回字符串、整型、日期等值以進行比較。
* @param list
* @param method
* @param reverseFlag
*/
public void sortByMethod(List<E> list, final String method, final boolean reverseFlag) {
Collections.sort(list, new Comparator<Object>() {
@SuppressWarnings("unchecked")
public int compare(Object arg1, Object arg2) {
int result = 0;
try {
Method m1 = ((E) arg1).getClass().getMethod(method, null);
Method m2 = ((E) arg2).getClass().getMethod(method, null);
Object obj1 = m1.invoke(((E)arg1), null);
Object obj2 = m2.invoke(((E)arg2), null);
if(obj1 instanceof String) {
// 字符串
result = obj1.toString().compareTo(obj2.toString());
}else if(obj1 instanceof Date) {
// 日期
long l = ((Date)obj1).getTime() - ((Date)obj2).getTime();
if(l > 0) {
result = 1;
}else if(l < 0) {
result = -1;
}else {
result = 0;
}
}else if(obj1 instanceof Integer) {
// 整型(Method的返回參數可以是int的,因爲JDK1.5之後,Integer與int可以自動轉換了)
result = (Integer)obj1 - (Integer)obj2;
}else if(obj1 instanceof Long) {
// 整型(Method的返回參數可以是Long的)
Long o1 = (Long)obj1;
Long o2 = (Long)obj2;
result = Integer.parseInt(o1.toString()) - Integer.parseInt(o2.toString());
}else {
// 目前尚不支持的對象,直接轉換爲String,然後比較,後果未知
result = obj1.toString().compareTo(obj2.toString());
System.err.println("MySortList.sortByMethod方法接受到不可識別的對象類型,轉換爲字符串後比較返回...");
}
if (reverseFlag) {
// 倒序
result = -result;
}
} catch (NoSuchMethodException nsme) {
nsme.printStackTrace();
} catch (IllegalAccessException iae) {
iae.printStackTrace();
} catch (InvocationTargetException ite) {
ite.printStackTrace();
}
return result;
}
});
}
// 測試函數 false 正序 true 倒敘
public static void main(String[] args) throws Exception {
// 生成自定義對象,然後對它按照指定字段排序
List<StatChargingDto> listMember = new ArrayList<StatChargingDto>();
listMember.add(new StatChargingDto("11","111",1l));
listMember.add(new StatChargingDto("22","222",11l));
listMember.add(new StatChargingDto("33","333",11l));
System.out.println("Member當前順序...");
System.out.println(listMember);
MySortList<StatChargingDto> msList = new MySortList<StatChargingDto>();
msList.sortByMethod(listMember, "getChargingStationCount", false);
System.out.println("Member按字段數量排序後...");
System.out.println(listMember);
}
}