我正在努力研究如何從充滿對象的數組列表中獲取屬性。我想找到屬于某一餐的所有菜肴，并按 dishType 過濾這些菜肴，并將它們顯示在視圖的表格中。所以我寫了方法 getDishNameByType 但它會返回 null。任何幫助將不勝感激！Meal.Javapublic class Meal { @Id @GeneratedValue private Long id; @ManyToMany private Set<Dish> dishesList = new HashSet<>(); public String getDishNameByType(String dishType) { for (Dish dish : dishesList) { if (dishType == dish.getDishType()) { return dish.getDishName(); } } return null; }}Dish.Javapublic class Dish { @Id @GeneratedValue private Long id; private String dishName; private String dishType; @ManyToMany(mappedBy = "dishesList") private Set<Meal> mealsList = new HashSet<>();查看.html<tr th:if="${mealPage.empty}"> <td colspan="7" th:text="#{meals.list.table.empty}">No meals found</td></tr><tr th:each="meal : ${mealPage}"> <td th:text="${meal.id}">1</td> <td th:each="dish : ${meal.dishesList}" th:text="${meal.getDishNameByType("Maincourse")}"></td></tr>
1 回答
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TA貢獻1802條經驗 獲得超5個贊
如果你有兩個對象，obj1和obj2，那么obj1 == obj2當true且僅當這兩個對象完全相同時。
String foo = "abc";
String bar = "abc";
boolean same = (foo == bar); //false
boolean similar = (foo.equals(bar)); //true
所以你需要打電話equals：
public String getDishNameByType(String dishType) {
for (Dish dish : dishesList) {
if ((dishType.equals(dish.getDishType()))) {
return dish.getDishName();
}
}
return null;
}
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