I would use TreeMap, which implements SortedMap. It is designed exactly for that. Example: Map<Integer, String> map = new TreeMap<Integer, String>(); // Add Items to the TreeMap map.put(1, “One”); map.put(2, “Two”); map.put(3, “Three”); // Iterate over them for (Map.Entry<Integer, String> entry : map.entrySet()) { System.out.println(entry.getKey() + ” => ” + entry.getValue()); } See the Java … Read more
You can use a custom comparator like this: Comparator<String> secondCharComparator = new Comparator<String>() { @Override public int compare(String s1, String s2) { return s1.substring(1, 2).compareTo(s2.substring(1, 2)); } }; Sample: SortedMap<String,String> map = new TreeMap<String,String>(secondCharComparator); map.put(“Za”, “FOO”); map.put(“Ab”, “BAR”); map.put(“00”, “ZERO”); System.out.println(map); // prints “{00=ZERO, Za=FOO, Ab=BAR}” Note that this simply assumes that the String has … Read more
Here is a solution: public static <K, V extends Comparable<V>> Map<K, V> sortByValues(final Map<K, V> map) { Comparator<K> valueComparator = new Comparator<K>() { public int compare(K k1, K k2) { int compare = map.get(k2).compareTo(map.get(k1)); if (compare == 0) return 1; else return compare; } }; Map<K, V> sortedByValues = new TreeMap<K, V>(valueComparator); sortedByValues.putAll(map); return sortedByValues; … Read more
Until upcoming JSF 2.3, UIData components such as <h:dataTable>, <p:dataTable>, etc and <ui:repeat> does not support iterating over a Map. This is only supported in <c:forEach>. One way is to convert the map entries to an array (alone entrySet() won’t work as UIData also doesn’t support Set until upcoming JSF 2.3). <h:dataTable value=”#{bean.map.entrySet().toArray()}” var=”entry”> <h:column>#{entry.key}</h:column> … Read more
You can change the behaviour of ArrayList List<MyType> list = new ArrayList<MyType>() { public boolean add(MyType mt) { super.add(mt); Collections.sort(list, comparator); return true; } }; Note: a PriorityQueue is NOT a List, if you didn’t care what type of collection it was, the simplest would be to use a TreeSet, which is just like a … Read more
You can not sort TreeMap on values. A Red-Black tree based NavigableMap implementation. The map is sorted according to the natural ordering of its keys, or by a Comparator provided at map creation time, depending on which constructor is used You will need to provide comparator for Comparator<? super K> so your comparator should compare … Read more
According to your latest update. If you are using TreeMap Struts2 cannot correctly determine type of elements inside it. Change declaration of testTreeMap from TreeMap to Map. private Map<String,ObjectCList> testTreeMap = new TreeMap<String,ObjectCList>(); Or annotate testTreeMap with com.opensymphony.xwork2.util.Element annotation to tell Struts2 what type are elements inside map. @Element(value = ObjectCList.class) private TreeMap<String,ObjectCList> testTreeMap = … Read more