Need help with collection

[jay lai]

I have a Collection<Box> , I need to extract certain row from this collection base on some criteria. If number, name are the same, using the most recent statusDate (Date)

Ex:

public class Box implements Serializable

private Long id;

private String number;

private String name;

private Date statusDate;

so if the collection has the following items:

1   44444    Box1    09/20/2012
2   44444    Box1    08/10/2010
3   33333    Box3    08/08/2009
4   44444    Box1    07/01/2009
5   55555    Box5    01/01/2008

This is just sample make up. So I would like to have the final result as:
1   44444    Box1    09/20/2012 (because it has the most latest date)
3   33333    Box3    08/08/2009
5   55555    Box5    01/01/2008

Any ideas? 

I have the loops thru the collections, but not sure how to compare 
if (name the same && number the same) {
  if (statusDate is latest) 
{
   add item into new ArrayList();
}
}

Sincerely thanks and please help!!!

[Jeff Verdegan]

Your fist step is to figure out how you would do it "manually." What information do you need to keep track of? What operations do you need to perform? What decisions do you make? Describe the steps as precisely, thoroughly, and simply as possible, without regard to Java or computers--just as a general set of instructions. Once you have that, if you've done it correctly, translating it to Java will be relatively easy.

[jay lai]

Your fist step is to figure out how you would do it "manually." What information do you need to keep track of? What operations do you need to perform? What decisions do you make? Describe the steps as precisely, thoroughly, and simply as possible, without regard to Java or computers--just as a general set of instructions. Once you have that, if you've done it correctly, translating it to Java will be relatively easy.

Yes, I tried to, but still need some help....

[Jeff Verdegan]

jay lai wrote:

Your fist step is to figure out how you would do it "manually." What information do you need to keep track of? What operations do you need to perform? What decisions do you make? Describe the steps as precisely, thoroughly, and simply as possible, without regard to Java or computers--just as a general set of instructions. Once you have that, if you've done it correctly, translating it to Java will be relatively easy.

Yes, I tried to, but still need some help....

I can't help you unless you show some effort and ask a more detailed question. What did you try? Where did you get stuck?

[jay lai]

Here what I have tried so far, still not quite got the item that i need.
1. Sort the collection by name, then number then statusDate

public Collection<Box> findAllBox() {
// this list already sort as I mentioned above so the statusDate will be the first record among the one that have same name and same number
 Collection<Box> orgList = myService.findAllBox(); 
 Map<String,TreeSet<Box>> map = new HashMap<String,TreeSet<Box>>(); 
  TreeSet<Box> boxList = new TreeSet<Box>(new BoxComparator());
  
  // so loop thru the original list
  for (Box box : orgList) {
    boxList.add(box);
    map.put(box.getName(),boxList()); // add key as name and the TreeSet as values into Map
  }

  Collection<Box> finalresult = new ArrayList<Box>();
  for(Map.Entry<String,TreeSet<Box>> element: map.entrySet) {
 // i want to get the first item from each list but seems not working
   Box box = Collections.first(element.getValue());
   finalresult.add(box);

 }

return finalresult

}

// printout the result: seems getting the first item of collection and loop again and again, so i got same data repeat every row.

Anything i did wrong here???? Thanks

[R. Jain]

Only keep your codes inside your CodeTags for better readability..

[PrasannaKumar maddu]

By overriding Comparator OR Comparable interfaces methods you can achieve sorting your collection.Google the interfaces.

[jay lai]

PrasannaKumar maddu wrote:By overriding Comparator OR Comparable interfaces methods you can achieve sorting your collection.Google the interfaces.

The collection already sorted. The problem is I have the code above tryign to extract out 1 record of each name, number if they are similar

1. The list orglist already sorted by number, name and date

1   44444    Box1    09/20/2012  
2   44444    Box1    08/10/2010  
3   44444    Box1    07/01/2009  
4   33333    Box3    08/08/2009  
5   55555    Box5    01/01/2008
5   55555    Box5    01/01/2000  

2. I want to achieve this on my final result to display: (code list above but somehow not working)
1   44444    Box1    09/20/2012 (has 3 records the same  this one has the most current date)
4   33333    Box3    08/08/2009 
5   55555    Box5    01/01/2008 (has 2 record the same , this one has the most current date)

THNKS

public Collection<Box> findAllBox() {  
  // this list already sort as I mentioned above so the statusDate will be the first record among the one that have same name and same number  
  Collection<Box> orgList = myService.findAllBox();   
  Map<String,TreeSet<Box>> map = new HashMap<String,TreeSet<Box>>();   
  TreeSet<Box> boxList = new TreeSet<Box>(new BoxComparator());  
    
  // so loop thru the original list  
  for (Box box : orgList) {  
    boxList.add(box);  
    map.put(box.getName(),boxList()); // add key as name and the TreeSet as values into Map  
  }  
  
  Collection<Box> finalresult = new ArrayList<Box>();  
  for(Map.Entry<String,TreeSet<Box>> element: map.entrySet) {  
 // i want to get the first item from each list but seems not working  
   Box box = Collections.first(element.getValue());  
   finalresult.add(box);  
  
 }  
  
return finalresult  
  
}  

[K Abhijit]

there are multiple way you can handle this issue.

[MODERATOR ACTION: Deleted fully coded solution.]

K Abhijit, please remember that this site is NotACodeMill, and LetThemDoTheirOwnHomework. Thank you!

[jay lai]

K Abhijit wrote:there are multiple way you can handle this issue.

[MODERATOR ACTION: Deleted fully coded solution.]

K Abhijit, please remember that this site is NotACodeMill, and LetThemDoTheirOwnHomework. Thank you!

This site used to be a good, and construtive forum back there., that where people got stuck and ask for it. It is getting worse now!!!