Retrieving String Values through Integer values

Question

I have an Integer ArrayList with elements e.g. 60,45,60,15 - These are activity minutes. Each of these elements have an associated Activity Names. E.g. Activity A has time of 60, Activity B has time of 45, etc.

How to write a function in Java which given integer value, can return Activity Name? Initially I thought HashMap was correct, but since minutes can be duplicate, it overwrites the previous value if its same and I am not interested in implementing a custom Map similar to MultiValueMap of Guava collections.

Any clues to implement this helps.

EDIT 1:

I tried implementing as suggested by Wasi - however, I am getting IndexOutOfBoundsException. I am expecting both activities from mapping60, 1 activity from mapping15, and 1 activity from mapping45. What am I doing wrong?

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

public class MultiMapTest {

public static void main(String[] args) {

    Map<Integer, List<String>> map = new HashMap<Integer, List<String>>();

    List<String> activityMappings60 = new ArrayList<String>();
    activityMappings60.add("Act 1 60min");
    activityMappings60.add("Act 2 60min");

    List<String> activityMappings15 = new ArrayList<String>();
    activityMappings15.add("Act 3 sprint");
    activityMappings15.add("Act 4 sprint");

    List<String> activityMappings45 = new ArrayList<String>();
    activityMappings45.add("Act 5 45min");
    activityMappings45.add("Act 6 45min");


    map.put(new Integer(60), activityMappings60 );
    map.put(new Integer(15), activityMappings15 );
    map.put(new Integer(45), activityMappings45 );

    List<Integer> arrayInteger = Arrays.asList(60,60,15,45);

    for(Integer i=0; i < arrayInteger.size();i++) {
        System.out.println(map.get(arrayInteger.get(i)).get(i));
        System.out.println(map.get(arrayInteger.get(i)).remove(i));
    }

}

If there two activity with same integer value then which one's name you want? You can use HashMap<Integer, ArrayList<String>> and it should work for you. — Wasi Ahmad
– Wasi Ahmad, Commented Dec 11, 2016 at 7:15
you can create an object with 2 members activity and duration and fill them in an ArrayLsit, BUT, you need to solve the duplicate issue, even if you can have 2 records with same duration (say 60) and different activity names, then when giving duration 60 to the function which activity should be returned?? — Yazan
– Yazan, Commented Dec 11, 2016 at 7:20
any one of the activity should be returned - but once its returned, I want to remove it from the source list, so next call with 60 should return the other one. — Yogendra
– Yogendra, Commented Dec 11, 2016 at 7:26
since you maybe often make remove operation then you can use HashMap<Integer,LinkedList<Srting>> for it's more simple about remove operation. — nail fei
– nail fei, Commented Dec 11, 2016 at 7:29
i can see Wasi Ahmad sol is good, you can take that concept and wrap it in a class with basic operation [add(), remove(), find()]. — Yazan
– Yazan, Commented Dec 11, 2016 at 7:36

Arty Jiang · Accepted Answer · 2016-12-11 09:18:54Z

1

The only problem in your code is when get and remove from the activities list you should not use i. Use 0 instead to get and remove the first element always. This should work in your loop:

List<String> list = map.get(arrayInteger.get(i));
    if (list != null && !list.isEmpty()) {
        System.out.println(list.remove(0));
}

The output I got:

Act 1 60min
Act 2 60min
Act 3 sprint
Act 5 45min

The whole thing I use:

public static void main(String[] args) {
    Map<Integer, List<String>> map = new HashMap<Integer, List<String>>();

    List<String> activityMappings60 = new ArrayList<String>();
    activityMappings60.add("Act 1 60min");
    activityMappings60.add("Act 2 60min");

    List<String> activityMappings15 = new ArrayList<String>();
    activityMappings15.add("Act 3 sprint");
    activityMappings15.add("Act 4 sprint");

    List<String> activityMappings45 = new ArrayList<String>();
    activityMappings45.add("Act 5 45min");
    activityMappings45.add("Act 6 45min");

    map.put(new Integer(60), activityMappings60);
    map.put(new Integer(15), activityMappings15);
    map.put(new Integer(45), activityMappings45);

    List<Integer> arrayInteger = Arrays.asList(60, 60, 15, 45);

    for (Integer i = 0; i < arrayInteger.size(); i++) { // inside loop I use my code as above
        List<String> list = map.get(arrayInteger.get(i));
        if (list != null && !list.isEmpty()) {
            System.out.println(list.remove(0));
        }
    }

}

edited Dec 11, 2016 at 9:18

answered Dec 11, 2016 at 8:27

Arty Jiang

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2 Comments

Yogendra Over a year ago

Still getting the same IndexOutOfBoundException.

Yogendra Over a year ago

Did you try running it with the code I added? If yes, can you paste the entire example that you tested? May be I am not doing it right.

mazhar islam · Accepted Answer · 2017-01-19 17:45:10Z

1

I guess this is what you are looking for.

public static void main(String[] args) {
    HashMap<Integer, ArrayList<String>> duration_to_activity_map = new HashMap<>();

    ArrayList<String> activityList = new ArrayList<>();
    activityList.add("A");
    activityList.add("B");
    duration_to_activity_map.put(30, activityList);

    activityList = new ArrayList<>();
    activityList.add("C");
    activityList.add("D");
    duration_to_activity_map.put(60, activityList);

    System.out.println(duration_to_activity_map.toString());
}

It prints:

{60=[C, D], 30=[A, B]}

So, if you want the activities with duration 60, it will give you [C, D].

System.out.println(duration_to_activity_map.get(60)); // prints - [C, D]

Remove elements from ArrayList: See this tutorial. But as @cainiaofei said, LinkedList is better option as implementation of List interface since you need to remove elements.

edited Jan 19, 2017 at 17:45

mazhar islam

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answered Dec 11, 2016 at 7:19

Wasi Ahmad

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4 Comments

Yogendra Over a year ago

Kind of, but the minutes can be duplicate i.e. there could be multiple activities with value 60. So I want to return the first value and use it for printing and then remove this selected element from the list. Next time when other activity with 60 min comes, I want to retrieve the next value from the list.

Wasi Ahmad Over a year ago

@YogendraJ you can do that. just remove the element from ArrayList using index and return the first element from ArrayList every time when you need to print it.

Yogendra Over a year ago

I tried implementing the example as you suggested, but getting indexOutOfBoundsException. I have updated the question with my example. Can you point it where I am going wrong?

Yogendra Over a year ago

This is also correct answer and I was able to achieve what I needed. Thanks again, Wasi.

nail fei · Accepted Answer · 2016-12-11 07:43:35Z

0

just as Wasi Ahmad advice you can use Map<Integer,List> and since you maybe often make delete operation, i think use LinkedList is better.

here is a demo:

public void demo(){
    Map<Integer,List<String>> map = new HashMap<Integer,List<String>>();
    List<String> innerList = new LinkedList<String>();
    innerList.add("d1");
    innerList.add("d2");
    map.put(60, innerList);
    System.out.println(map.get(60).remove(0));
    System.out.println(map.get(60).remove(0));
}

answered Dec 11, 2016 at 7:43

nail fei

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