摘要：前言直接進入正題，閑的沒事把對對象集合排序進行了封裝，寫起來優雅一點，不用每次用的時候自己再一個比較器對象了。
前言
直接進入正題，閑的沒事把Java對對象集合排序進行了封裝，寫起來優雅一點，不用每次用的時候自己再new一個比較器對象了。
ListOrderUtil
沒多少東西，就是下邊這點代碼！
import java.lang.reflect.Field;
import java.util.*;
public class ListOrderUtil {
private List mArrayList;//數據集合
private LinkedHashMap mOrderList = new LinkedHashMap<>();//所有的排序字段
private Class mClass;//當天T的Class
public static int ORDER_ASC = 1;//正序排列
public static int ORDER_DESC = 2;//倒序排列
public ListOrderUtil(List arrayList, Class tClass) {
this.mArrayList = arrayList;
this.mClass = tClass;
}
/**
* 設置排序字段（按照設置的先后順序對其進行排序）
*
* @param fieldName 字段名稱
* @param orderPattern 排序模式
* @return
*/
public ListOrderUtil setOrderField(String fieldName, int orderPattern) {
this.mOrderList.put(fieldName, orderPattern);
return this;
}
/**
* 對數據集合進行排序
*
* @return
*/
public List order() {
this.mArrayList.sort(new Comparator() {
@Override
public int compare(T o1, T o2) {
Field field = null;
int order = 0;
for (Map.Entry item : mOrderList.entrySet()) {
try {
field = mClass.getDeclaredField(item.getKey());
field.setAccessible(true);
if (field == null) {
throw new NoSuchFieldException(item.getKey());
}
if (item.getValue() == ORDER_ASC) {
order = field.get(o1).toString().compareTo(field.get(o2).toString());
} else {
order = field.get(o2).toString().compareTo(field.get(o1).toString());
}
if (order != 0) {
return order;
}
} catch (Exception e) {
e.printStackTrace();
}
}
return 0;
}
});
return this.mArrayList;
}
}
使用案例
首先是對象一枚！
import java.util.Comparator;
public class Students {
private int studentId;
private int age;
private String studentName;
public Students() {
}
public Students(int studentId, int age, String studentName) {
this.studentId = studentId;
this.age = age;
this.studentName = studentName;
}
public int getStudentId() {
return studentId;
}
public void setStudentId(int studentId) {
this.studentId = studentId;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getStudentName() {
return studentName;
}
public void setStudentName(String studentName) {
this.studentName = studentName;
}
}
先來看看不封裝的時候如何排序：
大量的邏輯處理代碼冗余......
public class Main {
public static void main(String[] args) {
//添加測試數據
ArrayList students = new ArrayList<>();
Students students1 = new Students(1001, 22, "djk");
Students students2 = new Students(1002, 18, "xxh");
Students students3 = new Students(1003, 31, "wyd");
Students students4 = new Students(1002, 18, "wxz");
Students students5 = new Students(1005, 19, "sxn");
Students students6 = new Students(1004, 32, "ljc");
students.add(students1);
students.add(students2);
students.add(students3);
students.add(students4);
students.add(students5);
students.add(students6);
//-------------不封裝的寫法----------------------------不堪入目啊！！！！
//1、使用studentId正序排列
Collections.sort(students, new Comparator() {
@Override
public int compare(Students o1, Students o2) {
return o1.getStudentId() - o2.getStudentId();
}
});
//2、使用studentId和age進行多字段排序,studentId正序為首，若想等便以age進行倒序排列。
Collections.sort(students, new Comparator() {
@Override
public int compare(Students o1, Students o2) {
int order = o1.getStudentId() - o2.getStudentId();
if (order == 0) {
order = o2.getAge() - o1.getAge();
}
return order;
}
});
//3、多字段排序
Collections.sort(students, new Comparator() {
@Override
public int compare(Students o1, Students o2) {
int order = o1.getStudentId() - o2.getStudentId();
if (order == 0) {
order = o2.getAge() - o1.getAge();
}
if (order == 0) {
order = o2.getStudentName().compareTo(o1.getStudentName());
}
return order;
}
});
}
}
再來看看封裝后的：
舒服多了......
public class Main {
public static void main(String[] args) {
//添加測試數據
ArrayList students = new ArrayList<>();
Students students1 = new Students(1001, 22, "djk");
Students students2 = new Students(1002, 18, "xxh");
Students students3 = new Students(1003, 31, "wyd");
Students students4 = new Students(1002, 18, "wxz");
Students students5 = new Students(1005, 19, "sxn");
Students students6 = new Students(1004, 32, "ljc");
students.add(students1);
students.add(students2);
students.add(students3);
students.add(students4);
students.add(students5);
students.add(students6);
//排序使用
ListOrderUtil listOrderUtil = new ListOrderUtil<>(students, Students.class);
//1、使用studentId正序排列
listOrderUtil.setOrderField("studentId", ListOrderUtil.ORDER_ASC).order();
//2、使用studentId和age進行多字段排序,studentId正序為首，若想等便以age進行倒序排列。
listOrderUtil.setOrderField("studentId", ListOrderUtil.ORDER_ASC)
.setOrderField("age", ListOrderUtil.ORDER_DESC);
//3、多字段排序
listOrderUtil.setOrderField("studentId", ListOrderUtil.ORDER_ASC)
.setOrderField("age", ListOrderUtil.ORDER_DESC)
.setOrderField("studentName", ListOrderUtil.ORDER_DESC)
.order();
}
}
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