what collection class to use??

[Dar Var]

I have a method that returns a TreeMap.

The TreeMap stores values as follows:
{a=String[] of values,
b=String[] of values,
c=String[] of values}

However now I need to return an alias string aswell i.e. I want to return a meaningful name for each key a, b and c etc.

Is there any Collection that can store something like (key, keyName, values) or do I have to use an Object for each key to store the key:alias pairs.
If so how can TreeMap sort by these Object keys

Hope I've made sense.

[Bauke Scholtz]

If you want to store same groups of values, you'd better to wrap the values in a DTO (Data Transfer Object). Such a DTO is nothing more than a Class with the desired fields and the appropriate getters and setters. Then you can store more DTO's in any Collection or Map object.

Sorting can be done by a Comparator. Or implement Comparable in the DTO.

DTO example:

public class MyData {
    private long id;
    private String value1;
    private String value2; 
 
    // And all appropriate public getters and setters here.
 
    // Eventually add a constructor like:
    public MyData(long id, String value1, String value2) {
        this.id = id;
        this.value1 = value1;
        this.value2 = value2;
    }
}

A map of DTO's

Map<MyData> dtos = new TreeMap<MyData>();
dtos.add(new MyData(1, "value1a", "value1a"));
dtos.add(new MyData(2, "value2a", "value2b"));
dtos.add(new MyData(3, "value3a", "value3b"));

[ October 17, 2006: Message edited by: Bauke Scholtz ]

[Dar Var]

You cannot add an Object to a Map like this.

dtos.add(new MyData(1, "value1a", "value1a"));

The only method TreeMap provides is put(Object o1, Object o2)

[Bauke Scholtz]

This was just a stupid example Use a Set instead. HashSet for example. Or a List. Or if you want to use keys, then put the identifier as key in the map, like: map.put(1, new MyDto());

[Ken Blair]

Originally posted by Dar Var:
I have a method that returns a TreeMap.

The TreeMap stores values as follows:
{a=String[] of values,
b=String[] of values,
c=String[] of values}

However now I need to return an alias string aswell i.e. I want to return a meaningful name for each key a, b and c etc.

Is there any Collection that can store something like (key, keyName, values) or do I have to use an Object for each key to store the key:alias pairs.
If so how can TreeMap sort by these Object keys

Hope I've made sense.

Using a simple container for the key that can also provide a meaningful String is definitely one option. Another option would be to use the meaningful String as the key though that may not be feasible or desirable for a number of reasons. Yet another possibility is to have a second Map that maps each key to a meaningful String value.

So to answer your question: no, there's nothing like that in Collections. Bauke already alluded to using Comparable with the container object to solve your sorting issue. You might find something like that available somewhere like apache.org under Commons. There's a number of other options as well, a few of which I expressed earlier.