Question

（重新定义方法

public Collection<String> values();

）

我有一张地图包含在另一张地图中，所以就像这样：

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

（实习生地图是subjectGradeMap）我现在想要使用这种方法：

public Collection<String> values()

获取包含地图所有值的集合。我试过了：

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

但它不起作用。试过这个：

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

但徒劳无功：-S

这个问题解决了谢谢！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;
}

你有什么想法吗？

Entry类是以下类，（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());
            }

    }

谢谢你的帮助！

Answer 1

centralMap.values()会返回一个Collection，Collection没有values()。 centralMap.values()基本上会返回地图列表。因此，为了评估每个地图，您需要迭代：

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

构建centralMap中包含的所有地图中所有值的集合：

List myGrandList = new ArrayList();
for (Map map : centralMap.values()) {
    myGrandList.addAll(map.values());
}
return myGrandList;

Answer 2

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：

原始版本：http://commons.apache.org/collections/apidocs/org/apache/commons/collections/map/MultiKeyMap.html
with-generic 版本（更好）：http://sourceforge.net/projects/collections

嵌套在集合中的地图..获取值（）设置地图2D

2 个答案: