java8 根据类的某些属性进行去重操作

朴灿烈づ我的快乐病毒、 2022-04-05 17:55 321阅读 0赞

1.  import java.util.ArrayList;
2.  import java.util.Comparator;
3.  import java.util.List;
4.  import java.util.TreeSet;
5.  import java.util.stream.Collectors;
6.  
7.  public class Person \{
8.  private Integer id;
9.  private String firstName;
10. private String secondName;
11. 
12. /\*\*
13. \*
14. \*/
15. public Person() \{
16. super();
17. \}
18. 
19. /\*\*
20. \* @param id
21. \* @param firstName
22. \* @param secondName
23. \*/
24. public Person(Integer id, String firstName, String secondName) \{
25. super();
26. this.id = id;
27. this.firstName = firstName;
28. this.secondName = secondName;
29. \}
30. 
31. /\*
32. \* (non-Javadoc)
33. \* @see java.lang.Object\#equals(java.lang.Object)
34. \*/
35. @Override
36. public boolean equals(Object obj) \{
37. if (this == obj) \{
38. return true;
39. \}
40. if (obj == null) \{
41. return false;
42. \}
43. if (getClass() != obj.getClass()) \{
44. return false;
45. \}
46. Person other = (Person) obj;
47. if (firstName == null) \{
48. if (other.firstName != null) \{
49. return false;
50. \}
51. \} else if (!firstName.equals(other.firstName)) \{
52. return false;
53. \}
54. if (id == null) \{
55. if (other.id != null) \{
56. return false;
57. \}
58. \} else if (!id.equals(other.id)) \{
59. return false;
60. \}
61. if (secondName == null) \{
62. if (other.secondName != null) \{
63. return false;
64. \}
65. \} else if (!secondName.equals(other.secondName)) \{
66. return false;
67. \}
68. return true;
69. \}
70. 
71. /\*\*
72. \* @return the firstName
73. \*/
74. public String getFirstName() \{
75. return firstName;
76. \}
77. 
78. /\*\*
79. \* @return the id
80. \*/
81. public Integer getId() \{
82. return id;
83. \}
84. 
85. /\*\*
86. \* @return the secondName
87. \*/
88. public String getSecondName() \{
89. return secondName;
90. \}
91. 
92. /\*
93. \* (non-Javadoc)
94. \* @see java.lang.Object\#hashCode()
95. \*/
96. @Override
97. public int hashCode() \{
98. final int prime = 31;
99. int result = 1;
100. result = prime \* result + ((firstName == null) ? 0 : firstName.hashCode());
101. result = prime \* result + ((id == null) ? 0 : id.hashCode());
102. result = prime \* result + ((secondName == null) ? 0 : secondName.hashCode());
103. return result;
104. \}
105. 
106. /\*\*
107. \* @param firstName
108. \* the firstName to set
109. \*/
110. public void setFirstName(String firstName) \{
111. this.firstName = firstName;
112. \}
113. 
114. /\*\*
115. \* @param id
116. \* the id to set
117. \*/
118. public void setId(Integer id) \{
119. this.id = id;
120. \}
121. 
122. /\*\*
123. \* @param secondName
124. \* the secondName to set
125. \*/
126. public void setSecondName(String secondName) \{
127. this.secondName = secondName;
128. \}
129. 
130. /\*
131. \* (non-Javadoc)
132. \* @see java.lang.Object\#toString()
133. \*/
134. @Override
135. public String toString() \{
136. return "Person \[id=" + id + ", firstName=" + firstName + ", secondName=" + secondName + "\]";
137. \}
138. 
139. public static void main(String\[\] args) \{
140. Person p1 = new Person(1, "wang", "gang");
141. Person p2 = new Person(2, "wang", "qiang");
142. Person p3 = new Person(3, "wang", "cheng");
143. Person p4 = new Person(4, "wang", "qiang");
144. Person p5 = new Person(5, "wang", "cheng");
145. List<Person> list = new ArrayList<>();
146. list.add(p1);
147. list.add(p2);
148. list.add(p3);
149. list.add(p4);
150. list.add(p5);
151. System.out.println(list);
152. /\*
153. \* output:
154. \* \[Person \[id=1, firstName=wang, secondName=gang\], Person \[id=2,
155. \* firstName=wang, secondName=qiang\], Person \[id=3, firstName=wang,
156. \* secondName=cheng\]\]
157. \*/
158. List<Person> distinctList = list.stream()
159. .collect(Collectors.collectingAndThen(Collectors.toCollection(
160. // 利用 TreeSet 的排序去重构造函数来达到去重元素的目的
161. // 根据firstName去重
162. () -> new TreeSet<>(Comparator.comparing(Person::getFirstName))), ArrayList::new));
163. /\*
164. \* output:
165. \* \[Person \[id=1, firstName=wang, secondName=gang\]\]
166. \*/
167. System.out.println(distinctList);
168. 
169. List<Person> distinctList1 = list.stream().collect(Collectors
170. .collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(o -> \{
171. // 根据firstName和secondName进行去重
172. return o.getFirstName() + "," + o.getSecondName();
173. \}))), ArrayList::new));
174. /\*
175. \* output:
176. \* \[Person \[id=3, firstName=wang, secondName=cheng\], Person \[id=1,
177. \* firstName=wang, secondName=gang\], Person \[id=2, firstName=wang,
178. \* secondName=qiang\]\]
179. \*/
180. System.out.println(distinctList1);
181. 
182. TreeSet<Person> set = new TreeSet<>(Comparator.comparing(o -> \{
183. // 根据firstName和secondName进行去重
184. return o.getFirstName() + "," + o.getSecondName();
185. \}));
186. set.addAll(list);
187. /\*
188. \* output:
189. \* \[Person \[id=3, firstName=wang, secondName=cheng\], Person \[id=1,
190. \* firstName=wang, secondName=gang\], Person \[id=2, firstName=wang,
191. \* secondName=qiang\]\]
192. \*/
193. System.out.println(set);
194. \}
195. \}