multimap

This is kind of stupid but how do I install MultiMap ? I need a way to store multiple values to keys and my map implementation isn't working dimo414 That class, MultiMap , is not part of the Java standard library. It is part of Apache Commons , a separate set of utility classes many Java developers find useful. An alternate Multimap implementation (which I would recommend) is available in Guava , Google's utility library. In either case, in order to use these classes, you need to download the jar distributed by the project, and add it to your classpath when you run your program. You can do

I want to use a std::multimap container, but I need to know that it will always maintain order, as in the first element in will be the first element iterated over and the second will always be the second. What I'm asking is this: Is std::multimap< key, value > equivalent to std::vector< std::pair< const key, std::vector< value > > > Marius Bancila A multimap is not the equivalent of a vector, not in terms of implementation. Multimaps are usually implemented as a binary search tree. The elements of a multimap are always kept in a sorted order by their key following a strict weak order criteria

Apparently you could do either, but the former is more common. Why would you choose the latter and how does it work? I read this: http://www.drdobbs.com/cpp/stls-red-black-trees/184410531 ; which made me think that they did it. It says: insert_always is a status variable that tells rb_tree whether multiple instances of the same key value are allowed. This variable is set by the constructor and is used by the STL to distinguish between set and multiset and between map and multimap. set and map can only have one occurrence of a particular key, whereas multiset and multimap can have multiple

Is there a way to covert the below to using collectors yet? List<String[]> lines = getLines(); Multimap<String,String> multimap = ArrayListMultimap.create(); lines.forEach(line -> multimap.put(line[0],line[1]); ); You can use Multimaps.toMultimap collector: ListMultimap<String, String> multimap = lines.stream() .collect(Multimaps.toMultimap( l -> l[0], l -> l[1], ArrayListMultimap::create )); Or if you don't need mutability, use ImmutableListMultimap.toImmutableListMultimap collector: ListMultimap<String, String> multimap = lines.stream() .collect(toImmutableListMultimap(l -> l[0], l -> l[1]))

i want to serialize and deserialize a MultiMap (Apache Commons 4) using JSON. Piece of code to test: MultiMap<String, String> map = new MultiValueMap<>(); map.put("Key 1", "Val 11"); map.put("Key 1", "Val 12"); map.put("Key 2", "Val 21"); map.put("Key 2", "Val 22"); ObjectMapper mapper = new ObjectMapper(); String jsonString = mapper.writeValueAsString(map); MultiMap<String, String> deserializedMap = mapper.readValue(jsonString, MultiValueMap.class); The serialization works fine and results in a format I would expect: {"Key 1":["Val 11","Val 12"],"Key 2":["Val 21","Val 22"]} Unfortunately the

Has anyone ever used Multimaps on Android is it possible? Guava works as-is on Android. What problems did you have? Use the released JAR, not the Guava sources. And as always, you should be using ProGuard as part of your build process to trim the size of your final binary down. 来源： https://stackoverflow.com/questions/5168505/google-collections-on-android

I have a Multimap<Date,Invoice> multimap = ArrayListMultimap.create(); from guava. I was wondering how to SORT the the Date key in the multimap. Currently, I'm doing this: Iterator<Date> dateItr = multimap.keySet().iterator(); Set<Date> treeSet = new TreeSet<Date>(Collections.reverseOrder()); and later I loop through the treeSet iterator. Any idea how to avoid this circumvention? Guava team member here. Use TreeMultimap , or if you need to map into List s, use MultimapBuilder : return MultimapBuilder.treeKeys().arrayListValues().build() 来源： https://stackoverflow.com/questions/10589716/how-to