如何检查Map中的键是否以给定的String值开头

Question

I'm looking for a method like:

myMap.containsKeyStartingWith("abc"); // returns true if there's a key starting with "abc" e.g. "abcd"

or

MapUtils.containsKeyStartingWith(myMap, "abc"); // same

I wondered if anyone knew of a simple way to do this

Thanks

Answer 1

This can be done with a standard SortedMap :

Map<String,V> tailMap = myMap.tailMap(prefix);
boolean result = (!tailMap.isEmpty() && tailMap.firstKey().startsWith(prefix));

Unsorted maps (eg HashMap ) don't intrinsically support prefix lookups, so for those you'll have to iterate over all keys.

Answer 2

从地图中，您可以获得一组键，如果它们是String，您可以迭代Set的元素并检查startsWith("abc")

Answer 3

To build on Adel Boutros answer/comment about the efficiency of iterating keys, you could encapsulate key iteration in a Map subclass or decorator.

Extending HashMap would give you a class to put the method in and keep map-specific code out of your method, so lowering complexity and making the code more natural to read.