hashmap排序JAVA
package Mone;
import java .util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
public class SortMapByValues {
public static void main(String[] args) {
Map<String,Integer> aMap = new HashMap<String,Integer>();
// adding keys and values
aMap.put("Five", 5);
aMap.put("Seven", 7);
aMap.put("Eight", 8);
aMap.put("One",1);
aMap.put("Two",2);
aMap.put("Three", 3);
sortMapByValues(aMap);
}
private static void sortMapByValues(Map<String, Integer> aMap) {
Set<Entry<String,Integer>> mapEntries = aMap.entrySet();
System.out.println("Values and Keys before sorting :");
for(Entry<String,Integer> entry : mapEntries) {
System.out.println(entry.getValue() + " - "+ entry.getKey());
} // used linked list to sort, because insertion of elements in linked list is faster than an array list.
List<Entry<String,Integer>> aList = new LinkedList<Entry<String,Integer>>(mapEntries);
// sorting the List
Collections.sort(aList, new Comparator<Entry<String,Integer>>() {
@Override
public int compare(Entry<String, Integer> ele1, Entry<String, Integer> ele2) {
return ele1.getValue().compareTo(ele2.getValue());
}
}
); // Storing the list into Linked HashMap to preserve the order of insertion.
Map<String,Integer> aMap2 = new LinkedHashMap<String, Integer>();
for(Entry<String,Integer> entry: aList) {
aMap2.put(entry.getKey(), entry.getValue());
} // printing values after soring of map
System.out.println("Value " + " - " + "Key");
for(Entry<String,Integer> entry : aMap2.entrySet()) {
System.out.println(entry.getValue() + " - " + entry.getKey()); }
}
}