CODEWITHSUNDEEP
javahashmapcomparatortreemapcomparable
jaggs
jaggs

Reputation: 308

Sorting values in a tree map with string and list bean as parameters

Continuation from my previous question posted Sorting a map in java

I am trying out a solution to sort a tree map based on its values

Let me declare the Map 

Map<String, List<Bean>> sortedBeanMap =new TreeMap<String,List<Bean>>();

i have created a separate comparator method to compare the values .

 public class MapSort {
    public static Map sortByValue(Map unsortedMap){

    Map sortedMap = new TreeMap(new ValueComparator(unsortedMap));
    sortedMap.putAll(unsortedMap);
    return sortedMap;
  }
  public static Map sortByKey(Map unsortedMap){
    Map sortedMap = new TreeMap();
    sortedMap.putAll(unsortedMap);
    return sortedMap;
  }
}

ValueComparator class

 public class ValueComparator implements Comparator {
  Map map;

  public ValueComparator(Map map){
    this.map = map;
  }
  public int compare(Object keyA, Object keyB){

    Comparable valueA = (Comparable) map.get(keyA);
    Comparable valueB = (Comparable) map.get(keyB);

    System.out.println(valueA +" - "+valueB);

    return valueA.compareTo(valueB);

  }
}

I knew the values should be of type string for the comparable to Work.But in my case , it will be a bean list.So how to get the comparator to work for my case ?

i am stuck in this for a while ..Any suggestions and ideas would be great .

Thanks guys in advance...

Upvotes: 0

Views: 518

Answers (1)

ErstwhileIII
ErstwhileIII

Reputation: 4843

Since this is homework full code won't be supplied.

You are on the right track. Do create a class for your objects and implement the required methods for Comparable. You can decide what the "order" should be for two of your objects that have a list of beans: should on be smaller than another because the number of list elements are less; because the individual list elements have names that are "smaller"; or another well-defined ordering?

Upvotes: 1

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