How can I copy an ArrayList in Java?

Question

ArrayList<String> x = new ArrayList<String>(); 
for(int i = 0; i < x.size(); i++)
{
    ArrayList<String> x.get(i) = new  ArrayList<String>();
}

Both ArrayLists should be declared globally

The x ArrayList values are: server,buser,paer cook, runner, etc.

The first ArrayList value should be second ArrayList name(variable)

`ArrayList x.get(i) = new ArrayList();` _doesn't compile..._ — ldam, Sep 25 '18 at 11:12
The code you posted is invalid (it produces compiler errors) and it is not clear what exactly your question is. Please edit your question, post valid code, and explain more clearly what exactly your question is. — Jesper, Sep 25 '18 at 11:12
@MaëlPedretti how to use hashmap in this scenario can u explain. i am new to hashmap — Saravanan, Sep 25 '18 at 11:15
@Saravanan selenium is a testing framework how is this question related to that ? — Lokesh Pandey, Sep 25 '18 at 11:15
https://beginnersbook.com/2013/12/hashmap-in-java-with-example/ Also check GiorgosDev comment — Maël Pedretti, Sep 25 '18 at 11:18
@Saravanan but your question is related to java not testing right ? So why tag Selenium ? — Lokesh Pandey, Sep 25 '18 at 11:19
If you want each entry in `x` to be a `ArrayList`, declare `x` as `ArrayList> x = new ArrayList<>();` — Kevin Anderson, Sep 25 '18 at 11:19

GiorgosDev · Answer 1 · 2018-09-25T11:18:38.807

4

It is not possible to set variable names dynamically in Java. If you still want to give some description to arrays of string you can create a Map for instance. i.e.

ArrayList<String> x = new  ArrayList<String>(); 
Map<String, ArrayList<String>> vars = new HashMap()<>;
for(int i = 0; i<x.size(); i++)
{
    vars.put(x.get(i),new  ArrayList<String>());
}

...

vars.get("server").add("Some Server info");

edited Sep 25 '18 at 11:18

answered Sep 25 '18 at 11:11

GiorgosDev

1,757
1
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score 1 · Answer 2 · answered Sep 25 '18 at 11:30

First typeof x isn't ArrayList<String>, it is ArrayList<ArrayList> because x's element is ArrayList

Second, you can't set element of ArrayList with ArrayList.get, you should use ArrayList.set

ArrayList<ArrayList> x = new ArrayList<>();

//todo something with size of `x` (if not x.size() = 0)
for (int i = 0; i < x.size(); i++) {
    x.set(i, new ArrayList<String>());
}

score 1 · Answer 3 · answered Sep 25 '18 at 11:31

Try like this, You cannot create variable name dynamically.

public static void main(String[] args) {
        List<String> x = new ArrayList<>(Arrays.asList("server", "buser", "paer cook", "runner"));
        Map<String, ArrayList<String>> map = new HashMap<>();

//       if java version is 8
        x.forEach(eachElem -> {
            map.put(eachElem, new ArrayList<>());
        });

//      if java version is < 8
//      for(String eachElement : x ){
//          map.put(eachElement, new ArrayList<>());
//      }
    }

How can I copy an ArrayList in Java?

3 Answers3