根据指定字段进行去重

  • 简介（Introduction）：

    1、处理一个数组的数据
    2、根据对象的某个字段的值，进行去重操作

  • 快速上手（Getting Started）：
    数据模型

     1 [{
 2         "name": "name0",
 3         "age": "00",
 4         "sex": "00",
 5         "recodeNumber": 0
 6     },
 7     {
 8         "name": "name0",
 9         "age": "00",
10         "sex": "00",
11         "recodeNumber": 0
12     },
13     {
14         "name": "name1",
15         "age": "01",
16         "sex": "01",
17         "recodeNumber": 1
18     }, {
19         "name": "name2",
20         "age": "02",
21         "sex": "02",
22         "recodeNumber": 2
23     }, {
24         "name": "name3",
25         "age": "03",
26         "sex": "03",
27         "recodeNumber": 3
28     }, {
29         "name": "name4",
30         "age": "04",
31         "sex": "04",
32         "recodeNumber": 4
33     }, {
34         "name": "name5",
35         "age": "05",
36         "sex": "05",
37         "recodeNumber": 5
38     }, {
39         "name": "name6",
40         "age": "06",
41         "sex": "06",
42         "recodeNumber": 6
43     }, {
44         "name": "name7",
45         "age": "07",
46         "sex": "07",
47         "recodeNumber": 7
48     }, {
49         "name": "name8",
50         "age": "08",
51         "sex": "08",
52         "recodeNumber": 8
53     }, {
54         "name": "name9",
55         "age": "09",
56         "sex": "09",
57         "recodeNumber": 9
58     }
59 ]
    View Code

    • 1、实体类建立

       1 package demo.pojo;
 2 
 3 public class Field {
 4 
 5     /**
 6      * 名称
 7      */
 8     private String name;
 9 
10     /**
11      * 年龄
12      */
13     private String age;
14 
15     /**
16      * 性别
17      */
18     private String sex;
19 
20     /**
21      * 字段序号
22      */
23     private int recodeNumber;
24 
25 
26     public String getName() {
27         return name;
28     }
29 
30     public void setName(String name) {
31         this.name = name;
32     }
33 
34     public String getAge() {
35         return age;
36     }
37 
38     public void setAge(String age) {
39         this.age = age;
40     }
41 
42     public String getSex() {
43         return sex;
44     }
45 
46     public void setSex(String sex) {
47         this.sex = sex;
48     }
49 
50     public int getRecodeNumber() {
51         return recodeNumber;
52     }
53 
54     public void setRecodeNumber(int recodeNumber) {
55         this.recodeNumber = recodeNumber;
56     }
57 }
      View Code
    • 2、创建数据
       1 private static List<Field> getDemoData() {
 2         List<Field> fieldList = new LinkedList<>();
 3 
 4 
 5         for (int i = 0; i < 10; i++) {
 6 
 7 
 8             Field field = new Field();
 9 
10             field.setAge("0" + i);
11 
12             field.setName("name" + i);
13 
14             field.setRecodeNumber(i);
15 
16             field.setSex("0" + i);
17 
18             fieldList.add(field);
19 
20         }
21 
22         return fieldList;
23     }
      View Code
    • 3、核心方法
       1 public static List<demo.pojo.Field> getDistinctField(List<demo.pojo.Field> fieldList) {
 2         Map<Integer, demo.pojo.Field> fieldMap = new HashMap<Integer, demo.pojo.Field>();
 3 
 4         List<demo.pojo.Field> result = new LinkedList<>();
 5 
 6         for (demo.pojo.Field field1 : fieldList) {
 7 
 8             int recodeNumber = field1.getRecodeNumber();
 9 
10             for (int i = 0; i < fieldList.size(); i++) {
11                 if (fieldMap.containsKey(recodeNumber)) {
12                     continue;
13                 }
14 
15                 fieldMap.put(recodeNumber, field1);
16             }
17 
18         }
19 
20         for (Map.Entry<Integer, demo.pojo.Field> integerFieldEntry : fieldMap.entrySet()) {
21 
22             result.add(integerFieldEntry.getValue());
23         }
24 
25         return result;
26     }
      View Code
    • 4、测试
       1 public class TestOrderData {
 2 
 3 
 4     public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
 5 
 6         List<Field> fieldList = getDemoData();
 7 
 8 
 9         Field field = new Field();
10 
11         field.setAge("0");
12 
13         field.setName("name0");
14 
15         field.setRecodeNumber(0);
16 
17         field.setSex("0");
18 
19         // 添加一个重复的数据
20         fieldList.add(field);
21 
22         // 打印当前数组样式
23         System.out.println("添加数据后:" + new Gson().toJson(fieldList));
24 
25 
26         // 去重
27 
28         List<Field> distinctField = ListUtils.getDistinctField(fieldList);
29 
30         System.out.println("去重后:" + new Gson().toJson(distinctField));
31 
32     }
33 }
      View Code
    • 入门篇（Basics）：
      • 环境准备（Prerequisite）：
        JDK1.8
      • 安装（Installation）：
        IDEA 2019
      • 存在问题（Configuration）：
        暂无

    • 进阶篇（Advanced)：

    • 1、抽出公共方法

       1 package demo.util;
 2 
 3 import java.lang.reflect.Field;
 4 import java.util.HashMap;
 5 import java.util.LinkedList;
 6 import java.util.List;
 7 import java.util.Map;
 8 
 9 public class ListUtils<T> {
10 
11 
12     /**
13      * 一般去重方法
14      *
15      * @param fieldList 传入数组
16      * @return 去重后数组
17      */
18     public static List<demo.pojo.Field> getDistinctField(List<demo.pojo.Field> fieldList) {
19         Map<Integer, demo.pojo.Field> fieldMap = new HashMap<Integer, demo.pojo.Field>();
20 
21         List<demo.pojo.Field> result = new LinkedList<>();
22 
23         for (demo.pojo.Field field1 : fieldList) {
24 
25             int recodeNumber = field1.getRecodeNumber();
26 
27             for (int i = 0; i < fieldList.size(); i++) {
28                 if (fieldMap.containsKey(recodeNumber)) {
29                     continue;
30                 }
31 
32                 fieldMap.put(recodeNumber, field1);
33             }
34 
35         }
36 
37         for (Map.Entry<Integer, demo.pojo.Field> integerFieldEntry : fieldMap.entrySet()) {
38 
39             result.add(integerFieldEntry.getValue());
40         }
41 
42         return result;
43     }
44 
45 
46     /**
47      * 任意类型指定字段去重
48      *
49      * @param fieldList 传入数组
50      * @param fieldName 字段名称
51      * @return 去重后结果
52      * @throws NoSuchFieldException   产生异常
53      * @throws IllegalAccessException 产生异常
54      */
55     public List<T> getDistinctT(List<T> fieldList, String fieldName) throws NoSuchFieldException, IllegalAccessException {
56         Map<Integer, T> fieldMap = new HashMap<Integer, T>();
57 
58         List<T> result = new LinkedList<T>();
59 
60         int recodeNumber = 0;
61 
62         for (T field1 : fieldList) {
63 
64             Field[] declaredFields = field1.getClass().getDeclaredFields();
65 
66 
67             for (Field declaredField : declaredFields) {
68 
69                 if (declaredField.getName().equals(fieldName)) {
70 
71                     declaredField.setAccessible(true);
72 
73                     if (declaredField.get(field1) != null) {
74                         recodeNumber = Integer.valueOf(declaredField.get(field1).toString());
75                     }
76                 }
77             }
78 
79 
80             for (int i = 0; i < fieldList.size(); i++) {
81                 if (fieldMap.containsKey(recodeNumber)) {
82                     continue;
83                 }
84 
85                 fieldMap.put(recodeNumber, field1);
86             }
87 
88         }
89 
90         for (Map.Entry<Integer, T> integerTEntry : fieldMap.entrySet()) {
91 
92             result.add(integerTEntry.getValue());
93         }
94 
95         return result;
96     }
97 }
      View Code
    • 2、升级方法为任意类型数组的指定字段去重
       1 /**
 2      * 任意类型指定字段去重
 3      *
 4      * @param fieldList 传入数组
 5      * @param fieldName 字段名称
 6      * @return 去重后结果
 7      * @throws NoSuchFieldException   产生异常
 8      * @throws IllegalAccessException 产生异常
 9      */
10     public List<T> getDistinctT(List<T> fieldList, String fieldName) throws NoSuchFieldException, IllegalAccessException {
11         Map<Integer, T> fieldMap = new HashMap<Integer, T>();
12 
13         List<T> result = new LinkedList<T>();
14 
15         int recodeNumber = 0;
16 
17         for (T field1 : fieldList) {
18 
19             Field[] declaredFields = field1.getClass().getDeclaredFields();
20 
21 
22             for (Field declaredField : declaredFields) {
23 
24                 if (declaredField.getName().equals(fieldName)) {
25 
26                     declaredField.setAccessible(true);
27 
28                     if (declaredField.get(field1) != null) {
29                         recodeNumber = Integer.valueOf(declaredField.get(field1).toString());
30                     }
31                 }
32             }
33 
34 
35             for (int i = 0; i < fieldList.size(); i++) {
36                 if (fieldMap.containsKey(recodeNumber)) {
37                     continue;
38                 }
39 
40                 fieldMap.put(recodeNumber, field1);
41             }
42 
43         }
44 
45         for (Map.Entry<Integer, T> integerTEntry : fieldMap.entrySet()) {
46 
47             result.add(integerTEntry.getValue());
48         }
49 
50         return result;
51     }
      View Code
    • 3、测试比对
       1 package com.about.order;
 2 
 3 import com.google.gson.Gson;
 4 import demo.pojo.Field;
 5 import demo.util.ListUtils;
 6 
 7 import java.util.*;
 8 
 9 public class TestOrderData {
10 
11 
12     public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
13 
14         List<Field> fieldList = getDemoData();
15 
16 
17         Field field = new Field();
18 
19         field.setAge("0");
20 
21         field.setName("name0");
22 
23         field.setRecodeNumber(0);
24 
25         field.setSex("0");
26 
27         // 添加一个重复的数据
28         fieldList.add(field);
29 
30         // 打印当前数组样式
31         System.out.println("添加数据后:" + new Gson().toJson(fieldList));
32 
33 
34         // 去重
35 
36         List<Field> distinctField = ListUtils.getDistinctField(fieldList);
37 
38         List<Field> distinctField2 = new ListUtils<Field>().getDistinctT(fieldList, "recodeNumber");
39 
40         System.out.println("去重后:" + new Gson().toJson(distinctField));
41         System.out.println("去重后2:" + new Gson().toJson(distinctField2));
42 
43     }
44 
45 
46     private static List<Field> getDemoData() {
47         List<Field> fieldList = new LinkedList<>();
48 
49 
50         for (int i = 0; i < 10; i++) {
51 
52 
53             Field field = new Field();
54 
55             field.setAge("0" + i);
56 
57             field.setName("name" + i);
58 
59             field.setRecodeNumber(i);
60 
61             field.setSex("0" + i);
62 
63             fieldList.add(field);
64 
65         }
66 
67         return fieldList;
68     }
69 
70 
71 }
      View Code
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原文地址：https://www.cnblogs.com/liuyangfirst/p/13792947.html