java 如何根据条目集过滤地图条目
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how can I filter map entries based on set of entries
提问by brainydexter
I'm using google guava 12 and have a map:
我正在使用 google guava 12 并有一张地图：
Map<OccupancyType, BigDecimal> roomPrice;
I have a Set:
我有一套：
Set<OccupancyType> policy;
How can I filter entries in the roomPrice mapbased on policyand return the filtered map ?
如何过滤roomPrice map基于中的条目policy并返回过滤后的地图？
filteredMapneeds to have all the values from policy. In case, roomPrice map doesnt have an entry from policy, I'd like to input default value instead.
filteredMap需要拥有policy. 如果 roomPrice 地图没有来自政策的条目，我想输入默认值。
回答by Francisco Paulo
Since you have a Set of keys you should use Maps.filterkeys(), also Guava provides a pretty good set of predicates that you can use out of the box. In your case something like Predicates.in()should work.
由于您有一组键，您应该使用Maps.filterkeys()，Guava 还提供了一组非常好的谓词，您可以开箱即用。在你的情况下像Predicates.in()应该工作。
So basically you end up with:
所以基本上你最终得到：
Map<OccupancyType, BigDecimal> filteredMap
= Maps.filterKeys(roomPrice, Predicates.in(policy));
Hope it helps.
希望能帮助到你。
回答by Jeshurun
- Override and implement
equalsandhashcodeinOccupancyType. - Loop through
roomPrice's keyset and collect the elements contained in the filter.
Something like this:
像这样的东西：
Map<OccupancyType, BigDecimal> filteredPrices = new HashMap<OccupancyType, BigDecimal>();
for(OccupancyType key : roomPrice.keySet()) {
if(policy.contains(key) {
filteredPrices.put(key, roomPrice.get(key));
}
}
Update
更新
Ok after reading up a bit on Google Guava, you should be able to do something like:
好吧，在谷歌番石榴上读了一点之后，你应该能够做这样的事情：
Predicate<OccupancyType> priceFilter = new Predicate<OccupancyType>() {
public boolean apply(OccupancyType i) {
return policy.contains(i);
}
};
and then
接着
return Maps.filterValues(roomPrice, priceFlter);
should do the trick.
应该做的伎俩。
