Java store list to array

Question

I'm trying to read CSV file like this:

1,0,0,0,2,0,0,2,
0,2,0,0,0,0,0,5,
0,0,0,0,0,0,5,0,

This is my expected outcome:

[1, 5, 8]
[2, 8,]
[7]

This is my Java coding:

CSVReader a = new CSVReader(new FileReader("CM.csv"));
List<String[]> aa = a.readAll();

List<Integer> list = new ArrayList<>(); 
Object[] CM = new Object[3];

for (int i = 0; i < aa.size(); i++) {
    for (int x = 0; x < aa.get(i).length-1; x++) {
        if ( Integer.parseInt(aa.get(i)[x].trim()) >= 1 ){
                list.add(x+1);
            }
        }            
        CM[i] = list;
        list.clear();
    }

for (int i = 0; i < CM.length; i++) {
    System.out.print(CM[i]);
    System.out.print("\n");
    }

But I get Null outcome. If I delete the list.clear() line then get weird outcome like this :

[1, 5, 8, 2, 8, 7]
[1, 5, 8, 2, 8, 7]
[1, 5, 8, 2, 8, 7]

I want to store the list into the array, please ignore the way how i read the CSV file...

Two things: 1. How do you actually get to that output? 2. You should use better variable names than a and aa. — BradyK
– BradyK, Commented Oct 9, 2014 at 17:28
Explain what you are trying to do so we can help you...u have the excel input now what do you want to do with the excel input? — brso05
– brso05, Commented Oct 9, 2014 at 17:31

Prasad Khode · Accepted Answer · 2014-10-09 18:04:31Z

1

replace list.clear(); with list = new ArrayList<>();

you are assigning list to CM[i] and when you are calling list.clear() it clears the list and makes it empty list, as your CM variable is referring to list object, it wont have any values in it.

To get the values:

for (int i = 0; i < CM.length; i++) {
    List dataList = (List) CM[i];
    for (int j = 0; j < dataList.size(); j++) {
        // do your stuff
        System.out.println(dataList.get(j));
    }
}

edited Oct 9, 2014 at 18:04

answered Oct 9, 2014 at 17:32

Prasad Khode

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4 Comments

user3832964 Over a year ago

1 more question, how can i access the list value of the each array CM?? if i use CM[i].list[j] it does't work

user3832964 Over a year ago

for (int i = 0; i < CM.length; i++) { List datalist = (List)CM[i]; for (int j = 0; j < datalist.size(); j++) { System.out.print(CM[i].get(i)[j]); } } I do like this but can't......

user3832964 Over a year ago

I'm not prefer to create a new listdata. But can make it access to the CM[i] and list? like CM[i].list[i]

Prasad Khode Over a year ago

here you are not creating any new list object, you are just referring to the existing list object. in that case you can use System.out.print(CM[i].get(j)); with in second loop

brso05 · Accepted Answer · 2014-10-09 17:57:31Z

1

public class Location {
   private int x = 0;
   private int y = 0;

   public Location(int x, int y)
   {
       this.x = x;
       this.y = y;
   }

   public int getX()
   {
       return this.x;
   }
   public int getY()
   {
       return this.y.
   }

}


CSVReader csvReader = new CSVReader(new FileReader("CM.csv"));
List<String[]> records = csvReader.readAll();

ArrayList<Location> locations = new ArrayList<Location>();

for(int i = 0; i < records.size(); i++)
{
    for(int j = 0; j < records.get(i).length; j++)
    {
        if(Integer.parseInt(records.get(i)[j]) > 0)
        {
             locations.add(new Location(i,j));
        }
    }
}

Now all your locations will be stored in the locations arraylist. All you have to do is loop through that and get your coordinates for the records arraylist.

edited Oct 9, 2014 at 17:57

answered Oct 9, 2014 at 17:39

brso05

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9 Comments

user3832964 Over a year ago

My question is focus on how to store the list into the array, not shortcut my coding, pls ignore how i read the input

brso05 Over a year ago

This is exactly how you store the list into an array. This answers your question try the code.

user3832964 Over a year ago

read again my question, i have edited maybe u can see the diff

brso05 Over a year ago

I've read it several times it makes no sense what you are trying to do.

brso05 Over a year ago

If you want to store the locations where the number is greater than 1 then just create a location class with x and y and store those objects in an arraylist. Your question is very unclear as to what you are trying to do or why you are trying to do it. Based on what you said in the comments this answer is correct. You need to be more clear about what you are asking then we can better help you.

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