Java convert ArrayList to int array

Question

I want to convert my arraylist to a double array[]. Why can't I cast with this method, what is wrong?

public static void convert(ArrayList list, double array[]) {



    array = new double [list.size()];

    for (int x = 0; x < list.size(); x++) {

        array[x]=(double) list.get(x);

    }

}

I get this error message

String cannot be cast to java.lang.Double

I have this peace of code that does not work if I change fropm raw type ArrayList to Double, maybe suggestions to change this code?

getTest().addAll(Arrays.asList(line.split(",")));

What type of values should be in ArrayList list? Are they doubles? For the sake of clarity, can you provide a code snippet which uses your convert function? — John M
– John M, Commented Jun 9, 2015 at 19:12
I provided the piece of code, it reads from a file and saves the integers to an arraylist. — Tapani Yrjölä
– Tapani Yrjölä, Commented Jun 9, 2015 at 19:21

Safwan Hijazi · Accepted Answer · 2015-06-09 19:05:56Z

2

use this:

array[x]=Double.parseDouble(list.get(x));

answered Jun 9, 2015 at 19:05

Safwan Hijazi

2,0892 gold badges19 silver badges29 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Masud Parves Bhuiyan Over a year ago

How this will compile? Double.parseDouble takes String argument. list.get(x) returns Object.

Safwan Hijazi Over a year ago

this convert string to double

Safwan Hijazi Over a year ago

this line to convert string to double in correct way to avoid String cannot be cast to java.lang.Double, so I tried to change code and fix it

mefi · Accepted Answer · 2015-06-09 19:05:27Z

1

Exception message says it - your ArrayList contains String values. You should use generics as ArrayList<String> to prevent this runtime failures

answered Jun 9, 2015 at 19:05

mefi

1,2631 gold badge12 silver badges16 bronze badges

Comments

Razib · Accepted Answer · 2015-06-09 19:19:45Z

0

You can not apply casting on String to make it double like this -

array[x]=(double) list.get(x);

Your list is an ArrayList of Stirng. So you have to convert the each String item from the list to double like this -

public static void convert(ArrayList list, double array[]) {

    array = new double [list.size()];

    for (int x = 0; x < list.size(); x++) {

       array[x]=Double.parseDouble((String)list.get(x));

    }
}

edited Jun 9, 2015 at 19:19

answered Jun 9, 2015 at 19:16

Razib

11.2k12 gold badges59 silver badges86 bronze badges

Comments

Tapani Yrjölä · Accepted Answer · 2015-06-09 19:26:52Z

0

Ive got the idea. I just convert my ArrayList to ArrayList Then your code examples will work same as mine...

answered Jun 9, 2015 at 19:26

Tapani Yrjölä

1681 gold badge4 silver badges15 bronze badges

Comments

Masud Parves Bhuiyan · Accepted Answer · 2015-06-09 19:41:39Z

0

Use this code:

public static void convert(ArrayList list, double array[]) {

    array = new double [list.size()];

    for (int x = 0; x < list.size(); x++) 
    {
        Object value = list.get(x);
        if(value instanceof String)
        {
            array[x]=Double.parseDouble(value.toString());
        }
        else if(value instanceof Double)
        {
             array[x]=(double) list.get(x);
        }
        else if(value instanceof Integer)
        {
             array[x]=(int) list.get(x);
        }

    }    
}

edited Jun 9, 2015 at 19:41

answered Jun 9, 2015 at 19:36

Masud Parves Bhuiyan

2241 silver badge15 bronze badges

Collectives™ on Stack Overflow

Java convert ArrayList to int array

5 Answers 5

3 Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

3 Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related