java collection.sort help---urgent?

Question

I did the arraylist sort but on my eclipse it has an error, i dont know what happened? can anyone help me plz
public static void main(String[] args) {
ArrayList cAList = new ArrayList();
cAList.add(Color.red);
cAList.add(Color.orange);
cAList.add(Color.yellow);
cAList.add(Color.green);
cAList.add(Color.cyan);
cAList.add(Color.blue);
cAList.add(Color.magenta);
Collections.sort(cAList);
for(Color c : cAList)
System.out.println(c);
}
at the collection.sort(cAList) it has an error statement:
Multiple markers at this line
- Bound mismatch: The generic method sort(List) of type Collections is not applicable for the arguments (ArrayList). The
inferred type Color is not a valid substitute for the bounded parameter >
- Line breakpoint:A1 [line: 35] - main(String[])

help plz...

Answer 1

This forum should help you:

http://stackoverflow.com/questions/791429/java-sorting-object-in-arraylist

http://stackoverflow.com/questions/2784514/sort-arraylist-of-custom-objects-by-property



And this one is helpful:

http://www.albeesonline.com/blog/2008/10/16/sorting-an-arraylist-of-objects/

Answer 2

What are you expecting the output to be? Which color comes first in the list, and which is last?



Do you want them sorted alphabetically? So blue comes first and yellow is last? (What if I speak German and have different names for colors than you?)



Do you want them sorted by rainbow order? So red is first and blue is last?



Do you want them sorted by intensity? Not sure who would be first and last here.



Do you want them sorted from your most favorite to your least favorite color? No clue who would be first and last here either.



In order for something to be sortable in Java, it has to implement the Comparable interface. To implement Comparable, you have to write a function that compares 2 parameters to determine one is greater than or equal to the other.



So when they wrote the Color class in Java, and they thought about implementing Comparable, they probably asked the same questions I asked above. And they came to the conclusion that sorting colors is a quagmire. There is no 1 right way to do it. So they didn't implement Comparable. And if an object doesn't implement Comparable, it isn't sortable.



You will have to write your own implementation of Comparable and sort the colors in whatever way you think they should be sorted. Previous answer provided some links that should be useful if you decide you really need to do that.

Answer 3

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Answer 4

confusing subject. browse on to yahoo and bing. this may help!