found this tutorial at other website... it is very useful so i posted in my blog...
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package com.rajesh.context;
====
package com.rajesh.context;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map.Entry;
import java.util.Set;
import java.util.TreeMap;
/**
* How to sort HashMap in Java by keys and values.
* HashMap doesn't guarantee any order, so you cannot rely on it, even if
* it appear that it storing entries in a particular order, because
* it may not be available in future version e.g. earlier HashMap stores
* integer keys on the order they are inserted but from Java 8 it has changed.
*
* @author WINDOWS 8
*/
public class HashMapSorting{
public static void main(String args[]) throws ParseException {
// let's create a map with Java releases and their code names
HashMap<String, String> codenames = new HashMap<String, String>();
codenames.put("JDK 1.1.4", "Sparkler");
codenames.put("J2SE 1.2", "Playground");
codenames.put("J2SE 1.3", "Kestrel");
codenames.put("J2SE 1.4", "Merlin");
codenames.put("J2SE 5.0", "Tiger");
codenames.put("Java SE 6", "Mustang");
codenames.put("Java SE 7", "Dolphin");
System.out.println("HashMap before sorting, random order ");
Set<Entry<String, String>> entries = codenames.entrySet();
for(Entry<String, String> entry : entries){
System.out.println(entry.getKey() + " ==> " + entry.getValue());
}
// Now let's sort HashMap by keys first
// all you need to do is create a TreeMap with mappings of HashMap
// TreeMap keeps all entries in sorted order
TreeMap<String, String> sorted = new TreeMap<>(codenames);
Set<Entry<String, String>> mappings = sorted.entrySet();
System.out.println("HashMap after sorting by keys in ascending order ");
for(Entry<String, String> mapping : mappings){
System.out.println(mapping.getKey() + " ==> " + mapping.getValue());
}
// Now let's sort the HashMap by values
// there is no direct way to sort HashMap by values but you
// can do this by writing your own comparator, which takes
// Map.Entry object and arrange them in order increasing
// or decreasing by values
Comparator<Entry<String, String>> valueComparator = new Comparator<Entry<String,String>>() {
@Override
public int compare(Entry<String, String> e1, Entry<String, String> e2) {
String v1 = e1.getValue();
String v2 = e2.getValue();
return v1.compareTo(v2);
}
};
// Sort method needs a List, so let's first convert Set to List in Java
List<Entry<String, String>> listOfEntries = new ArrayList<Entry<String, String>>(entries);
// sorting HashMap by values using comparator
Collections.sort(listOfEntries, valueComparator);
LinkedHashMap<String, String> sortedByValue = new LinkedHashMap<String, String>(listOfEntries.size());
// copying entries from List to Map
for(Entry<String, String> entry : listOfEntries){
sortedByValue.put(entry.getKey(), entry.getValue());
}
System.out.println("HashMap after sorting entries by values ");
Set<Entry<String, String>> entrySetSortedByValue = sortedByValue.entrySet();
for(Entry<String, String> mapping : entrySetSortedByValue){
System.out.println(mapping.getKey() + " ==> " + mapping.getValue());
}
}
}
This is dummy text. It is not meant to be read. Accordingly, it is difficult to figure out when to end it. But then, this is dummy text. It is not meant to be read. Period.
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