从ArrayList中删除重复的自定义对象

Question

我很难从自定义对象的ArrayList中删除重复项。

删除重复项

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;
    } 

自定义对象等于（）

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;
    }

删除重复项后的输出

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

关于为什么它实际上没有删除重复项，有什么提示吗？或者它实际上是通过将副本替换为原始副本来删除副本？不知道这里发生了什么。

Answer 1

您还需要重写hashcode方法，因为集合使用它来分配元素，这样如果obj1.equals（OB2）==true那么obj1.hashcode () == obj2.hashcode（）也必须为真。

因此，如果你的对手是这样的：

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;
}

hashcode看起来像这样：

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