如何對Map 集合做sort

Java所提供的Map class並無提供任何排序(sort)的函式
所以必需自行撰寫，範例參考如下

   
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;


public class sortMap {
 public static void main(String[] args){
  
  Map<String, Integer> sortMap = new TreeMap<String, Integer>();
  sortMap.put("N1", 5);
  sortMap.put("N2", 3);
  sortMap.put("N3", 1);
  sortMap.put("N4", 2);
  sortMap.put("N5", 4);
  Collection<Integer> sortMapTmp = sortMap.values();
  
  System.out.println("--unsort Map--");
  printSortMap(sortMap);
  
  sortMap = sortMapByComparator(sortMap);
  
  System.out.println("--sorted Map--");
  printSortMap(sortMap);
 }
 
 private static Map<String, Integer> sortMapByComparator(Map<String, Integer> unsortMap){
  
  List<Entry<String, Integer>> list = new LinkedList<Entry<String, Integer>>(unsortMap.entrySet());
  
  // Sorting the list based on values
  Collections.sort(list, new Comparator<Entry<String, Integer>>()
  {
    public int compare(Entry<String, Integer> o1, Entry<String, Integer> o2)
    {
      //若要由小排到大
      //如果 o1 > o2 => 回傳  1
      //     o1 = o2 => 回傳  0 
      //     o1 < o2 => 回傳 -1
      return o1.getValue().compareTo(o2.getValue());
    }
  });
  
  Map<String, Integer> sortedMap = new LinkedHashMap<String, Integer>();
  for (Entry<String, Integer> entry : list)
        {
            sortedMap.put(entry.getKey(), entry.getValue());
        }
  
  return sortedMap;
 }
 
 private static void printSortMap(Map<String, Integer> sortMap){
  
  for(Entry<String, Integer> entry : sortMap.entrySet()){
   System.out.println("Key : " + entry.getKey() + " Value : "+ entry.getValue());
  }
 }
}

[Reference]
http://stackoverflow.com/questions/1448369/how-to-sort-a-treemap-based-on-its-values

Dimensions expected after this token

在宣告 Map 物件時, 需注意內部的<key, value>宣告用法
裡頭不得為常用的 int , 而必須是 Integer

否則會出現"Syntax error on token "int", Dimensions expected after this token "

Example:
(X) Map<String, int> list_test = new TreeMap<String, int>();
(O) Map<String, Integer> list_test = new TreeMap<String, Integer>();