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Jul 1, 2009 · Method #1: Iterating over entries using a For-Each loop. This is the most common method and is preferable in most cases. It should be used if you need both map keys and values in the loop. Map<Integer, Integer> map = new HashMap<Integer, Integer>(); for (Map.Entry<Integer, Integer> entry : map.entrySet()) {.
The official way to do this is to call map.entrySet(), which returns a set of Map.Entry, each of which contains a key and a value (entry.getKey() and entry.getValue()). In an idiosyncratic implementation, it might make some difference whether you use map.keySet(), map.entrySet() or something else.
Finally, you need to collect into a List: // Stream<V> --> List<V>. .collect(Collectors.toList()) If you have only one entry, use this instead (NOTE: this code assumes that there is a value; otherwise, use .orElse(); see the javadoc of Optional for more details): // Stream<V> --> Optional<V> --> V.
May 15, 2012 · 15. A HashMap doesn't maintain eny order between keys. A TreeMap orders its keys by their natural order, or by the order imposed by a comparator that you pass when constructing the map. So if you want to have Integer keys ordered in reverse order, construct the TreeMap this way: Map<Integer, List<String>> sortedMap =.
Dec 11, 2009 · UPDATE It can be done in a single line using Lambda expression in Java 8. map.entrySet().removeIf(e-> <boolean expression> ); I know this question is way too old, but there isn't any harm in updating the better way to do the things :)
In Java 1.8 (Java 8) this has become lot easier by using forEach method from Aggregate operations (Stream operations) that looks similar to iterators from Iterable Interface. Just copy paste below statement to your code and rename the HashMap variable from hm to your HashMap variable to print out key-value pair. HashMap<Integer,Integer> hm ...
Jun 18, 2015 · What's the best way to iterate over the below two maps together? I want to compare two maps values which are strings and have to get the keys and values. HashMap<String, String> map1; HashMa...
Feb 25, 2009 · Since this was the oldest question with the highest number of votes, it was the first I was offered when doing a search. Although this answer does not provide a Java 5 answer, it does answer the part of the question related to both easier and higher, since higher versions of Java do provide an easier option than Java 5 does. I can't help but ...
Mar 15, 2013 · Modifying the map clearly wasn't the issue in the question, as asked; if you have a problem using the Java HashMap with concurrent modification, please ask your question demonstrating that case. (Although you'll probably not run into whichever import issue caused the problem with the OP's code or something very similar.)
Oct 20, 2010 · Basically, I want to be able to access the keys by number, not by using the key's name. And I want to be able to access said key's value, to iterate over it. I'm imagining something like this: for(all keys in my hashmap) { for(int i=0; i < myhashmap.currentKey.getValue.size(); i++) { // do things with the hashmaps elements } }
