processing list of objects in Java

Question

I have a list of objects and i want to process subset of objects based on condition and then create a new list with processed objects.

The List if Objects

miss | shannon sperling
mr | john smith
prof | kim taylor
prof.dr | kim taylor

In the above list i want to the names which has two titles(kim taylor) and glue the title because prof is a subset of prof.dr. My final list should look like the following

miss | shannon sperling
mr | john smith
prof.dr | kim taylor

I tried with following code

void gluetitles(List title)
       {
           for (int i=0;i<title.size();i++) { 
                String names = (String) title.get(i);
                String[] titlename=names.split("\\|");\\split the list with delimiter and extracts titles and names
                String tle=titlename[0];
                String name=titlename[1];

           }     
       }

But i did not get idea how to compare and get the name which has two titles.

Consider using a map, and storing titleName[1] as the key and appending the new title if it doesn't already contain it. — David
– David, Commented Nov 7, 2013 at 9:04
i would like to glue the title of "prof kim taylor" and "prof.dr. kim taylor" into one "prof.dr.Kim taylor" — sara
– sara, Commented Nov 7, 2013 at 9:05
@MarcelPuyat An interesting thought, but she also hasn't said what would happen if a person had two titles such that neither contained the other. That wouldn't work if she wants the titles concatenated in some way. — Dennis Meng
– Dennis Meng, Commented Nov 7, 2013 at 9:20

David · Accepted Answer · 2013-11-07 09:43:18Z

1

This code works fine...

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

public class Notepad {

    public static void main(String args[]) {
        final List<String> titles = new ArrayList<>();
        titles.add("miss | shannon sperling");
        titles.add("mr | john smith");
        titles.add("prof | kim taylor");
        titles.add("prof.dr | kim taylor");
        gluetitles(titles);
    }

    static void gluetitles(final List<String> titles) {
        final Map<String, String> titleMap = new HashMap<>();
        for (final String names : titles) {
            final String[] titleName = names.split("\\|");
            final String title = titleName[0];
            final String name = titleName[1];
            if (doesMapContainName(titleMap, title, name)) {
                titleMap.put(name, title);
            }
        }
        for (final Entry<String, String> s : titleMap.entrySet()) {
            System.out.println("Name is " + s.getKey() + " Title is "
                    + s.getValue());
        }
    }

    private static boolean doesMapContainName(
            final Map<String, String> titleMap, final String title,
            final String name) {
        return (titleMap.get(name) != null && titleMap.get(name).length() < title
                .length()) || !titleMap.containsKey(name);
    }
}

The contain method is a bit dirty but the long and short of it is if it exists in the map, check if this new value is longer than the one we already know about, if it is, add it, if it doesn't exist in the map, add it. This assumes the data always just concatenates the titles like in the example, we have one with prof.dr and one with prof.

edited Nov 7, 2013 at 9:43

answered Nov 7, 2013 at 9:18

David

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3 Comments

sara Over a year ago

:How do i convert this titleMap back list with same format.When i tried to convert this map into list, the list prints either keys or values but not both.

David Over a year ago

You would need a print(Map<String, String>) method that just loops through the map, putting the key at the start, appending the pipe character and then append the value.

sara Over a year ago

Can i put the key,pipe char and value directly into list.add() or assign to string.Assign to sting works fine.But adding to list raising nullpointerexception

Jordi Reina · Accepted Answer · 2013-11-07 09:29:13Z

1

Here is the code that create a map with the name as a key and the title as value. After the map is created you should build the list you need concatening the value of the map with the key

 void gluetitles(List title)
    {
        Map<String, String> titleNamesMap = new TreeMap<String, String>();
        for (int i=0;i<title.size();i++) { 
             String names = (String) title.get(i);
             String[] titlename=names.split("\\|");//split the list with delimiter and extracts titles and names
             String tle=titlename[0];
             String name=titlename[1];
             if(titleNamesMap.containsKey(name)){
                 String oldTitle = titleNamesMap.get(name);
                 if(!oldTitle.contains(tle)){
                     String newTle = (tle+".").concat(oldTitle);
                     titleNamesMap.put(name,newTle);
                 }
             }else{
                 titleNamesMap.put(name, tle);
             }
        }
    }

Hope it will be useful for you.

edited Nov 7, 2013 at 9:29

answered Nov 7, 2013 at 9:17

Jordi Reina

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4 Comments

Dennis Meng Over a year ago

Concatenating the titles with . doesn't seem like the right way to go there, the example input I think gets prof.dr.prof | kim taylor with that approach instead of just prof.dr | kim taylor.

Jordi Reina Over a year ago

You're right. I didn't see that. The code should check if the new title is already in the map. I'll change the code. Thanks.

David Over a year ago

No it doesn't, if the order is prof.dr before prof in the list, you end up with prof .prof.dr - unless that's what you want.

sara Over a year ago

@david99world:yes you are true.Your code is working in other scenario too.

Marcel Puyat · Accepted Answer · 2013-11-07 09:10:26Z

0

You could use another for-loop within the for-loop you already have to compare the title of the current String to the title of other Strings in your list. You just have to make sure not to compare the string to itself by skipping over the same index with a continue. Like so:

void gluetitles(List title)
   {
       for (int i=0;i<title.size();i++) { 
            String names = (String) title.get(i);
            String[] titlename=names.split("\\|");
            String tle=titlename[0];
            String name=titlename[1];

            for (int j = 0; j < title.size(); j++) {
                if (j == i) continue; // This makes sure you don't compare it to itself.

                ...split the string here...

                if (secondTitle.contains(tle)) --> process what you want.
            }
       }     
   }

I'm not sure about the .contains method, but simply look for a String method that finds subsets.

answered Nov 7, 2013 at 9:10

Marcel Puyat

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1 Comment

Dennis Meng Over a year ago

.contains is fine, though if you are only interested if a string is a prefix of another, there's startsWith.

Prabhakaran Ramaswamy · Accepted Answer · 2013-11-07 09:14:00Z

0

Do like this

Your Comparator

class SimpleComparator implements Comparator<String> {
    @Override
    public int compare(String o1, String o2) {
        return o1.split("\\|")[1].trim().compareTo(o2.split("\\|")[1].trim());
    }
}

Your data

List<String> list = new ArrayList<String>();
list.add("miss | shannon sperling");
list.add("mr | john smith");
list.add("prof | kim taylor");
list.add("prof.dr | kim taylor");

Filtering the data

Set<String> s = new TreeSet<String>(new SimpleComparator());
s.addAll(list);
System.out.println(s);

output

mr | john smith
prof | kim taylor
miss | shannon sperling

answered Nov 7, 2013 at 9:14

Prabhakaran Ramaswamy

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Comments

blalasaadri · Accepted Answer · 2013-11-07 09:30:51Z

0

Basically what I would do is use a Map of some kind. That would look something like this:

void gluetitles(List<String> title) {
    Map<String, String> map = new HashMap<String,String>();
    for (int i=0;i<title.size();i++) { 
        String names = (String) title.get(i);
        String[] titlename = names.split("\\|");
        String tle = titlename[0];
        String name = titlename[1];

        if(map.containsKey(name)) {
            String savedTitle = map.get(name);
            if(isBetterTitle(tle, savedTitle)) { // compare your savedTitle to the given one here
                map.put(name, tle);
            }
        } else {
            map.put(name, tle);
        }
    }

    for(Iterator<String> it = map.keySet().iterator(); it.hasNext(); ) {
        String name = it.next();
        System.out.println(map.get(name) + name);
    }
}

boolean isBetterTitle(String tle1, String tle2) {
    return tle1.replaceAll(" ", "").contains(tle2.replaceAll(" ", ""));
}

edited Nov 7, 2013 at 9:30

answered Nov 7, 2013 at 9:15

blalasaadri

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1 Comment

Dennis Meng Over a year ago

For what it's worth, there's no need to call remove before put, put replaces any entry that was there with the entry that you give it.

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