How to make multiple lists with a loop in Java?

Question

So I would like to create multiple lists that have similar but different names.

So far I have:

for(int i=1; i<11; i++){
        String listName = String.format("listNumber%d", i);
        int[] listName;
    }

How can I change the third line so I would get listNumber1, listNumber2 etc

You want to change the variable name? Variable names cannot be changed programmatically and are there for readability. — CMilby
– CMilby, Commented Mar 3, 2016 at 15:52
Either make them into an array so you get listName[0], listName[1] etc. or make a list of lists. There is no way to dynamically generate a set of variable names. — Angelos Chalaris
– Angelos Chalaris, Commented Mar 3, 2016 at 15:54

bradimus · Accepted Answer · 2016-03-03 15:54:16Z

2

In short, you can't. You could create a map containing your arrays:

Map<String, int[]> listMap = new HashMap<>();

for(int i=1; i<11; i++){
    String listName = String.format("listNumber%d", i);
    listMap.put(listName, new int[arraySize]);
}

answered Mar 3, 2016 at 15:54

bradimus

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ouzman · Accepted Answer · 2016-03-04 06:49:01Z

1

You cannot use String on a variable name in Java.

If you want to use String to access a List, you can use Map;

Map<String, List<Integer>> lists = new HashMap<>();
lists.put("listNumber1", new ArrayList<Integer>());
lists.put("listNumber2", new ArrayList<Integer>());

lists.get("listNumber1").add(1);

But if you use String to itarate the lists, you can use array of List or List of List;

List<List<Integer>> lists = new ArrayList<>();
lists.add(new ArrayList<>());
lists.add(new ArrayList<>());

for(List<Integer> list : lists) {
    list.add(1);
}

edited Mar 4, 2016 at 6:49

answered Mar 3, 2016 at 16:03

ouzman

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