從ArrayList刪除重複的自定義對象

Question

我很難從自定義對象的ArrayList中刪除重複的項目。

刪除重複

public static ArrayList<UnchainedRestaurant> removeDuplicates(ArrayList<UnchainedRestaurant> arraylist) { 
     //remove any duplicates 
     ArrayList<UnchainedRestaurant> noDuplicates = new ArrayList<>(); 
     Set<UnchainedRestaurant> setItems = new LinkedHashSet<UnchainedRestaurant>(arraylist); 
     noDuplicates.addAll(setItems); 
     return noDuplicates; 
    } 

自定義對象的equals（）

public boolean equals(Object o) { 
     UnchainedRestaurant r = (UnchainedRestaurant) o; 
     String name1 = this.getName(); 
     String name2 = r.getName(); 

     name1 = Util.normalizeVenueName(name1); 
     name2 = Util.normalizeVenueName(name2); 

     if(name1.equals(name2)) { 
      return true; 
     } else return false; 
    } 

輸出刪除重複後

1. 786 Kebab & Curry 
2. Marlow's Tavern 
3. P.F. Chang's 
4. Ted's Montana Grill 
5. Which Wich? Superior Sandwiches 
6. Niko Niko Sushi 
7. Burger 21 
8. Tin Lizzys Bar and Grille 
9. Saigon Flavors 
10. Firehouse Subs 
11. Luigi's Pizza 
12. Roya Mediterranean Restaurant and Tapas Bar 
13. East Coast Wings & Grill 
14. Provino's Italian Restaurant 
15. Kani House 
16. Chow Baby 
17. Mimi's Cafe 
18. Monterrey Mexican Restaurant 
19. Panera Bread - Mall of Georgia 
20. Umami Asian Cuisine 
21. Parma Tavern 
7. Burger 21 -------------------------------- 
23. Luigi's A Slice of Italy 
4. Ted's Montana Grill -------------------------------- 
25. Tom + Chee - Buford 
2. Marlow's Tavern -------------------------------- 
1. 786 Kebab & Curry 
28. Sushi Niko Niko 
13. East Coast Wings & Grill 
3. P.F. Chang's -------------------------------- 
31. Turkish Kitchen 
32. The Cheesecake Factory 
17. Mimi's Cafe 
34. Aha Sushi 
15. Kani House 
3. P.F. Chang's -------------------------------- 
37. Teavana 
38. Williams-Sonoma 
39. Great Wraps 
40. Auntie Anne's Pretzels 
1. 786 Kebab & Curry -------------------------------- 
42. Bruster's Real Ice Cream 
43. Spencer Gifts 
44. Pretzelmaker 
45. Little Tokyo of Georgia Mall 
46. Great American Cookies 

關於爲什麼它實際上並沒有刪除重複的任何提示？或者它是否通過用原始文件替換重複文件來刪除重複文件？不知道這裏發生了什麼。

Answer 1

您還需要覆蓋hashcode方法，因爲該設置使用該方法分配元素，因此如果obj1.equals(obj2) == true則obj1.hashcode() == obj2.hashcode()也必須爲true。

因此，如果您的平等是這樣的：

public boolean equals(Object o) { 
    UnchainedRestaurant r = (UnchainedRestaurant) o; 
    String name1 = this.getName(); 
    String name2 = r.getName(); 

    name1 = Util.normalizeVenueName(name1); 
    name2 = Util.normalizeVenueName(name2); 

    if(name1.equals(name2)) { 
     return true; 
    } else return false; 
} 

的hashcode會看起來像這樣：

@Override 
public int hashcode() { 
    return Util.normalizeVenueName(this.getName()).hashcode(); 
}