Count duplicates in a TreeSet Collection

[Quiddo Quitch]

i was wondering, is there anyway to know how many duplicates were detected in a TreeSet Collection ?

for example in the following code there are 3 duplicates ... is there anyway to get that value ?

  
public class prueba {

  public static void main(String[] args) {

    TreeSet<Number> t1 = new TreeSet<Number>();
    t1.add(1);
    t1.add(1);
    t1.add(1);
    t1.add(1);

    for(Number s : t1){
    	System.out.println(s);
    }

  }
}

thanks !!

[Christophe Verré]

Methods usually return some useful information. Did you check what the add method of java.util.TreeSet returns ?

[Quiddo Quitch]

yes i checked the returns methods, i have the method "size()" to determine the number of elements in the collection, but that not give me the number of duplicates

[Quiddo Quitch]

i figure it out, you can close this thread ...

the solution is to count all elements and then rest it to size() method ... finally you get the duplicates number

[K. Tsang]

A set contains no duplicates. So the size() method won't help. In fact what does add() returns? boolean right? Now does add return false if you add integer 1 the 2nd time? if so you can have a variable to keep track of this and will return 3 in your code.

[Mike Simmons]

What if you count how many times add() was called? Then if, for example, add() was called 35 times, but the final size() is 28, there must have been 7 duplicates.

Or, what if you counted how many times add() returned true?

[Quiddo Quitch]

K. Tsang wrote:A set contains no duplicates. So the size() method won't help. In fact what does add() returns? boolean right? Now does add return false if you add integer 1 the 2nd time? if so you can have a variable to keep track of this and will return 3 in your code.

i used a List to count the total results and a Set to have no duplicates ... then i got the size() of List minus the size() of Set ... this is probably not the smartest way, but it worked like a charm xD

[Christophe Verré]

this is probably not the smartest way

Surely not You misunderstood my hint. K. Tsang described what I wanted to tell you : use add()'s return value to determine if an element was added or not.

[Rob Spoor]

Perhaps you should use a org.apache.commons.collections.Bag