how to store value into arraylist with some specific index in java

Question

I have value list such as

0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.10, 0.11, 0.12

and I want to store it into ArrayList with specific index like this

0.1, 0.2, 0.3, == Index 1

0.4, 0.5, 0.6, == Index 2

0.7, 0.8, 0.9, == Index 3

0.10, 0.11, 0.12, == Index 4

Thanks

Very unclear requirements, but does `List.set(index, value)` do what you want? — Andy Turner, Nov 15 '15 at 06:05
i dont have tried yet, i dont understand with this. because i want store that list with looping for — Putra Nurfajar, Nov 15 '15 at 06:07
can i do `List.set(index, value)` with looping for ? because the index is dynamic — Putra Nurfajar, Nov 15 '15 at 06:09

score 0 · Answer 1 · edited May 23 '17 at 10:30

0

ArrayList[][] array = {{0.1,0.2,0.3},{0.4,0.5,0.6},{0.7,0.8,0.9},{0.10,0.11,0.12}}

This is a multi-dimensional array

To set values:

array[0][0] = 0.1;
array[0][1] = 0.2;
array[1][0] = 0.4;
array[1][1] = 0.5;

...ect

Also see How to create a Multidimensional ArrayList in Java?

edited May 23 '17 at 10:30

Community

1
1

answered Nov 15 '15 at 06:11

JavaFox

61
14

Kumaresan Perumal · Answer 2 · 2015-11-15T06:25:12.740

0

you use array List and HaspMap for you requirement

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

public class Test {

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

        list.add(0.1);
        list.add(0.2);

        map.put("key", list);

        System.out.println(map.get("key").get(0));
    }   
}

edited Nov 15 '15 at 06:25

answered Nov 15 '15 at 06:12

Kumaresan Perumal

1,926
2
29
35

@ChiefTwoPencils : now i changed it. have a look at it. – Kumaresan Perumal Nov 15 '15 at 06:26

score 0 · Accepted Answer · answered Nov 15 '15 at 06:13

In an ArrayList<Double> a single index can have a single value.

If you want to store more than one value try using a ArrayList<ArrayList<Double>>.

If you want to store it in an index use .set(index, value)

ArrayList<Double> list = new ArrayList<>();

list.add(0.1);
list.add(0.2);
list.add(0.3);

ArrayList<ArrayList<Double>> mainList = new ArrayList();

mainList.set(0, list);

From your list I see that 3 values make a list.

double []values = {0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.10, 0.11, 0.12};

ArrayList<ArrayList<Double>> mainList = new ArrayList();
int k = 0;
for(int i = 0; i < values.length; i += 3)
{
  ArrayList<Double> list = new ArrayList();
  list.add(values[i]);
  list.add(values[i + 1]);
  list.add(values[i + 2]);

  mainList.set(k ++, list);
}

I appreciate for your answer . I'll try it. . Thanks . . – Putra Nurfajar Nov 15 '15 at 06:17 — Putra Nurfajar, Nov 15 '15 at 06:17

score 0 · Answer 4 · answered Nov 15 '15 at 06:20

In arrayList you can't keep multiple value in same index, it just doesn't work that way.

Based on your requirement, i think, you can design the data structure in two way -

1. Map

Map<Integer, List<Double>>

a map keeping index as key, and list of the items as value. Thus keep (1, [0.1, 0.2, 0.3]) means 1 index as key and corresponding list as value

2. List of User Defined Object

class IndexValue {
  int index;
  double value;
  IndexValue(int index, double value) {
     this.index = index;
     this.value = value;
  }
}

List<IndexValue> indexValueList = new ArrayList<>();
indexValueList.add(new IndexValue(1, .1));
indexValueList.add(new IndexValue(1, .2));
indexValueList.add(new IndexValue(1, .3));

Depending on what OP is trying to do, it could also be a Map, but: `Map`, with the values: `((0.1, 1), (0.2, 1), (0.3, 1), (0.4, 2), (0.5, 2), ...)`. But without knowing why he wants it, hard to say ... — AntonH, Nov 15 '15 at 06:37

how to store value into arraylist with some specific index in java

4 Answers4