java - 扩展 AbstractMap 让我看到 put 方法的 UnsupportedOperationException

Question

我正在尝试实现一个个人的abstractMap。我的项目中有两种类型的 map ，一种 <String , List<Box>>和一个<String , Box> (盒子是一个类，用于将元素及其数量封装起来)。但是当我尝试 map 的 put 方法时，它向我显示“UnsupportedOperationException - 如果此 map 不支持 put 操作”

这是 map 的抽象类

public abstract class TamagotchiMap<X> extends AbstractMap<String, X> {

  @Override
  public abstract Set<Entry<String, X>> entrySet();


  public abstract void attachCategories(Set<String> categories);


  public abstract void addItemForCategory(String category, Box box);


  public abstract String getCategory(Box box);


  public Collection<String> getAllCategories() {
    return this.keySet();
  }



}

还有两个类扩展了这个类

1)

public class InventoryMainMap extends TamagotchiMap<Box> {

private final Set<Entry<String, Box>> entry = new HashSet<>();

@Override
public Set<Entry<String, Box>> entrySet() {
    return entry;
}


@Override
public void attachCategories(final Set<String> categories) {
    for (String category: categories) {
        this.put(category, null);
    }
}



/**
 * 
 * @return main item for this category
 * @param category is the category of item
 */
public Box getMainItem(final String category) {
    return this.get(category);
}

@Override
public String getCategory(final Box box) {
    for (String category: this.getAllCategories()) {
        if (this.get(category).containsItem(box.getItem())) {
            return category;
        }
      }
    return null;
}

@Override
public void addItemForCategory(final String category, final Box box) {
    if (this.containsKey(category)) {
        this.replace(category, box);
    }
}
}

2)

public class ItemContainerMap extends TamagotchiMap<List<Box>> {

private final Set<Entry<String, List<Box>>> entry = new HashSet<>();

@Override
public Set<Entry<String, List<Box>>> entrySet() {
    return entry;
}

@Override
public String getCategory(final Box box) {
    for (String category: this.getAllCategories()) {
        for (Box boxIterator: this.get(category)) {
            if (boxIterator.containsItem(box.getItem())) {
                return category;
            }
         }
    }
    return null;
}

@Override
public void addItemForCategory(final String category, final Box box) {
    if (this.containsKey(category)) {
       if (!this.get(category).contains(box)) {
           System.out.println("nuovo item");
           this.get(category).add(box);
       } else {
           System.out.println("item esistente");
           this.get(category).stream().filter(iterBox -> iterBox.equals(box)).forEach(iterBox -> iterBox.increaseQuantity());
       }
    } else {
        throw new NoSuchElementException();
    }

}

@Override
public void attachCategories(final Set<String> categories) {
    for (String category: categories) {
        this.put(category, new LinkedList<Box>());
    }
}

}

当我这样做的时候

class Test {

   TamagotchiMap map = new ItemContainerMap();
   map.put(string, box); 

}

它让我看到了我已经说过的异常。好像看跌期权无法使用，你知道我错在哪里吗？

Answer 1

抛出 UnsupportedOperationException 是从 AbstractMap 继承的 put(K, V) 的默认实现。您可以自己实现它，或者让您的 TamagotchiMap 扩展一个具体的 Map 类，例如 HashMap 而不是 AbstractMap。