0

（重新定义方法

public Collection<String> values();

)

我有一个地图包含在另一个地图中，所以它是这样的：

Map<String,Map<String,String>> centralMap

（实习地图是subjectGradeMap）我现在想用这个方法：

public Collection<String> values()

获取包含地图所有值的集合。我试过：

Collection<String> returncoll = centralMap.values().values();

但它没有用。也试过这个：

Collection<Map<String,String>> collec = centralMap.values();
Collection<String> returncollection = collec.values();

但徒劳：-S

那个问题解决了谢谢！现在我想问你是否有想法，我应该如何实现Iterator方法？

/**
* Returns an Iterator, that pass through all the entries of the map. If
* something changes in the map, when it is being passed through all its'
* entries by the Iterator, we can't determinate the behaviour that will
* happen..
*
* @return An Iterator that pass through all entries. Every entry will be
*         returned as String-Tripel with its' three Elements row, column
*         and value.
*/
@Override
public Iterator<Entry> iterator() {
return null;
}

你有想法吗？

Entry 类如下，（在我用来创建 TrueStringMap2D 对象的接口中实现：

final class Entry
    {       
       /** First Key. */
        private final String key1;

       /** Second Key. */
        private final String key2;

       /** Value. */
        private final String value;

       /** Ctor for a tripel.
        * @param key1 1st key.
        * @param key2 2nd key.
        * @param value Value.
        */
        public Entry(final String key1, final String key2, final String value)
        {
            this.key1 = key1;
            this.key2 = key2;
            this.value = value;
        }

        public String getFirstKey()
        {
            return key1;
        }

        public String getSecondKey()
        {
            return key2;
        }

        public String getValue()
        {
                return value;
        }

        @Override public boolean equals(final Object anything)
        {
            if(anything == null)
                return false;
            if(getClass() != anything.getClass())
                return false;
            final Entry that = (Entry)anything;
            return Objects.equals(getFirstKey(), that.getFirstKey())
                   && Objects.equals(getSecondKey(), that.getSecondKey())
                   && Objects.equals(getValue(), that.getValue());
        }

        // CHECKSTYLE- Magic Number
        @Override public int hashCode()
        {
            int hash = 7;
            hash = 17 * hash + Objects.hashCode(getFirstKey());
            hash = 17 * hash + Objects.hashCode(getSecondKey());
            hash = 17 * hash + Objects.hashCode(getValue());
            return hash;
        }
        // CHECKSTYLE+ Magic Number

        @Override public String toString()
        {
            return String.format("(%s, %s, %s)", getFirstKey(), getSecondKey(), getValue());
            }

    }

感谢您的帮助！

4

2 回答 2

1

centralMap.values()给你一个 Collection，Collection 没有values(). centralMap.values()本质上返回一个地图列表。因此，为了评估这些地图中的每一个，您需要迭代：

for (Map map : cetralMap.values()) {
    Collection values = map.values();
    // do something with your values here
}

要从包含的所有映射中构建所有值的集合centralMap：

List myGrandList = new ArrayList();
for (Map map : centralMap.values()) {
    myGrandList.addAll(map.values());
}
return myGrandList;
于 2012-05-03T11:16:58.947 回答
0

您可以使用MultiKeyMap（来自Apache 的Commons-Collections）：

MultiKeyMap<String, String> map;
map.put("Key1", "Key2", "Value");
map.put("Key1", "Key3", "Value2");

for (Entry<MultiKey<String>, String> entry : map.entrySet()) {
    // TODO something
}

它有两个版本：

于 2012-05-03T11:27:58.053 回答