Stack to --> ArrayList Java

Question

I made a Stack and an ArrayList to make a research. Actually I want now to make my Stack replaced by an ArrayList, but how to transform a Stack into an ArrayList ? How is it going with push, pop ... ?

public static ArrayList<State> search(State finalstate)
{
    ArrayList<State> toreturn = new ArrayList<State>();
    Stack<State>mystack=new Stack<State>();
    mystack.push(initState);
    State currState;
    currState=initState;
    while(!mystack.isEmpty() && !currState.equals(finalstate) )
    {
        currState=mystack.pop();
        toreturn.add(currState);
        if(currState.vecinos.containsKey("up"))
        {
            mystack.push(currState).vecinos.get("up");
        }
        if(currState.vecinos.containsKey("down"))
        {
            mystack.push(currState).vecinos.get("down");
        }
        if(currState.vecinos.containsKey("left"))
        {
            mystack.push(currState).vecinos.get("left");
        }
        if(currState.vecinos.containsKey("right"))
        {
            mystack.push(currState).vecinos.get("right");
        }
    }
    
    return toreturn;
}

Well pop removes items from a Stack, and push adds items to a Stack. Why are you adding items to your Stack while copying to the List? What do you want in your List when the method completes? — Elliott Frisch
– Elliott Frisch, Commented Feb 4, 2015 at 5:14
What does that mean? You're modifying the Stack while you copy it... that is probably not what you want. — Elliott Frisch
– Elliott Frisch, Commented Feb 4, 2015 at 5:17

Evgeniy Dorofeev · Accepted Answer · 2015-02-04 05:16:07Z

35

Stack is a Collection, you can use ArrayList(Collection) constructor

list = new ArrayList(stack);

answered Feb 4, 2015 at 5:16

Evgeniy Dorofeev

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3 Comments

Wei Over a year ago

This is problematic. If we pushed stuff into Stack in this order: 1, 2, 3, 4, 5, then surprisingly the ArrayList will also end up as [1, 2, 3, 4, 5] whereas we probably expect [5, 4, 3, 2, 1]

pubsy Over a year ago

Yup, @Wei is right, this method results in reverse order for stack.

Mick Over a year ago

Collections.reverse(stack); // resolves the issue :)

Bishoy Melek · Accepted Answer · 2020-03-09 11:52:32Z

6

The simplest way I've found to convert a Stack into a List is using the following line:

List<Integer> stackToList = new ArrayList(stack);

However, this yields the stack reversed. Meaning, if your stack was 1, 2, 3 you would expect in the list 3, 2, 1 because that's the order the stack objects would be "popped". That's not the case though instead, you get 1, 2, 3. So, in order to get the expected output, you need to execute

Collections.reverse (stackToList);

This will reverse the list inline and give you 3, 2, 1

edited Mar 9, 2020 at 11:52

Bishoy Melek

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answered Jan 13, 2020 at 2:37

RodXander

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Comments

Pritam Banerjee · Accepted Answer · 2019-08-26 07:33:46Z

1

The above answer is not right, as the order will be reverse.
Instead you can just iterate like this:

Stack<State> stack = new Stack<>();
List<State> list = new ArrayList<>();
while(!stack.isEmpty()) { 
    list.add(stack.pop()); 
}

answered Aug 26, 2019 at 7:33

Pritam Banerjee

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Comments

Diego Borba · Accepted Answer · 2023-08-11 10:10:24Z

0

ArrayDeque from Deque interface can be used for this type of operation.

ArrayDeque is better to used then Stack.

Deque<Integer> d = new ArrayDeque<Integer>();
d.push(10);
d.push(20);
d.push(30);

ArrayList<Integer> list = new ArrayList<Integer>(d);
System.out.println(d.toString());
System.out.println(list.toString());

edited Aug 11, 2023 at 10:10

Diego Borba

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answered Aug 9, 2023 at 17:26

VNK

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Comments

Ankit Chauhan · Accepted Answer · 2021-08-16 06:27:20Z

-1

Use Deque instead,

Deque<Integer> deque = new ArrayDeque<>();
deque.push(1);
deque.push(2);
deque.push(3);
System.out.println(new ArrayList<>(deque)); // 3, 2, 1

answered Aug 16, 2021 at 6:27

Ankit Chauhan

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1 Comment

Md. Nowshad Hasan Over a year ago

I can convert the stack into an array-list with this line.

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