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Index › Programming Questions & Help › Syntax Questions › Sort objects in ArrayList by classmethod result
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Sort objects in ArrayList by classmethod result (Read 601 times)
TVS
Sort objects in ArrayList by classmethod result
Feb 6th, 2009, 3:34pm  
Hey people,

The situation: I have an ArrayList of 4 objects (of Class Line). Within this Class I have a method to determine the angle of this line (Line.getAngle).
Now I want to sort the 4 objects (Lines) from highest angle to lowest angle, and use this order to draw a polygon, so I need the ArrayList again in the main application.
How can I do this? Do I need to use the Comparable method? If so, how does this work, because I never used it before and after some short research I still do not see how I can sort from higher number to lower number...

Thanks in advance!
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PhiLho 
Re: Sort objects in ArrayList by classmethod resul
Reply #1 - Feb 6th, 2009, 5:18pm  
The sort array of objects by String inside variable thread discuss the topic at length. The last message shows how to invert the comparison...
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TVS
Re: Sort objects in ArrayList by classmethod resul
Reply #2 - Feb 6th, 2009, 5:39pm  
ok, sorry for starting this thread. I just kind of hoped there would be an easier way than the technique in that thread...
Thanks for pointing me to the right thread though
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PhiLho 
Re: Sort objects in ArrayList by classmethod resul
Reply #3 - Feb 6th, 2009, 9:01pm  
No problem.
And I fear there is no "simple" way to indicate which field(s) to use when comparing two arbitrary objects.
After all, if you define a Line object, you can sort by x, y of starting or ending point, by color, by angle as you want, by length, by thickness, and so on. Or even by a combination of some of these parameters.
The Comparator/Comparable way might seem complex, but once you understood how to use it, it isn't so much intimidating, and it is very flexible.
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