Thread: treemap Duplicates

hi!
i need help with the treemap, the problem is if i store 2 elements with the same key but different values, only the latest entry gets stored for example

        TreeMap map = new TreeMap();
        map.put(1, "alice");
        map.put(1, "bob");
        System.out.println(map.entrySet());

Displays:
run:
[1=bob]
BUILD SUCCESSFUL (total time: 0 seconds)

Expected Output
run:
[1=alice] [1=bob]
BUILD SUCCESSFUL (total time: 0 seconds)

is it possible to achieve the expected output??

thanks !

The Map interface does not allow duplicate keys...as per the API:

A map cannot contain duplicate keys; each key can map to at most one value.

There may be ways to achieve the behavior you want, such as storing Lists in your TreeMap rather than the String

There may be ways to achieve the behavior you want, such as storing Lists in your TreeMap rather than the String

can you elaborate please? thanks!

i want to use the treemap class to do something like:
(sort the names according to height if the height is same sort the names according to weight)

at the moment i am sorting objects, i.e i created a class with 5 fields, 2 keys for weight and height and 3 for storing the name, height, weight, implemented comparable, added the elements to an arraylist and invoked the sort function. this works fine, but treemap has lot of cool member functions that would help, plus easier to use rather than implementing comparable.

thanks for the post!

I am not fully sure what you wish to do but I'll guess that you want to store data that represents a person (name, height, weight, etc...). So you could write an object (call it say Person), that contains all those values as variables. From there you could a) add these to a TreeMap or b) add the to an ArrayList (the List would require the extra step up sorting after all is said and done, the TreeMap does this for you). Either way, in doing so you must implement the Comparable interface so you can order based upon height or weight. See Object Ordering (The Java™ Tutorials > Collections > Interfaces)