Problem in sorting using Comparator interface

Question

I have created a ArrayList of HashMap like

ArrayList<HashMap<?,?>>  var = new ArrayList<HashMap<?,?>>();

My HashMaps contains a String value "name" with key "name".What I want is to sort ArrayList by name so can I do this using Comparator? Please Help Me.

Ramesh PVK · Accepted Answer · 2011-06-02 06:49:02Z

3

        ArrayList<HashMap<String,String>>  var = new ArrayList<HashMap<String,String>>();
    Collections.sort(var, new Comparator(){

        public int compare(Object o1, Object o2)
        {
            Map map1 = (Map) o1;
            Map map2 = (Map)o2;
            String name1 = (String) map1.get("name");
            String name2 = (String) map2.get("name");
            if(name1 != null){
            return name1.compareTo(name2);
            } else if(name2 != null){
            return name2.compareTo(name1);
            }else{
             return 0;
            }
        }
    });

Here is the answer.

edited Jun 2, 2011 at 6:49

answered Jun 2, 2011 at 6:31

Ramesh PVK

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4 Comments

amit Over a year ago

the use of Map (and not Map<T1,T2>) - without generics is deprecated. also note no null check for map1.get("name"). but besides from it - this will do the trick.

Ramesh PVK Over a year ago

What i have written is just a template.

Rudy Over a year ago

Oh I just realize we can do that. :)

Ramesh PVK Over a year ago

@amit yes , i did that in the edit. So that anyone can try using the code directly.

gwood · Accepted Answer · 2011-06-02 07:03:32Z

1

You could try something like this.

public int compare(Object o1, Object o2) {
  String one = (String)((HashMap)o1).get("name");
  String two = (String)((HashMap)o2).get("name");
  return one.compareTo(two);
}

I haven't compiled this, so be sure to check its correct. =)

edited Jun 2, 2011 at 7:03

answered Jun 2, 2011 at 6:53

gwood

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