Java List list to String []

Question

How would I convert

List list= new ArrayList();

to

String [] profArr= {};

I have tried doing

profArr = list.toArrary() 

    and

profArr = (String [])list.toArrary()

I get the following error:

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.String;

I also have tried

String [] profArr= (String [])list.toArray(new String[0]);

and I get this error: The requested resource () is not available.

Here is how I create the list:

static List decode(int x)
    {
        List power2List = new ArrayList();
        if (x < 0) 
            throw new IllegalArgumentException("Decode does not like negatives");
        while (x > 0)
        {
            int p2 = Integer.highestOneBit(x);
            x = x - p2;
            power2List.add(p2);
        }
        return power2List;   
    }

List list= new ArrayList();
list= decode(rset.getInt("favprofs")); //rset being a result set which pulls one int

What is your original list of? Does it have a toString() Method implemented? — dann.dev
– dann.dev, Commented Mar 6, 2012 at 2:07
The message about "The requested resource () is not available." has nothing to do with this code; something weird just happened that one time. — Ernest Friedman-Hill
– Ernest Friedman-Hill, Commented Mar 6, 2012 at 2:08

Jeffrey · Accepted Answer · 2012-03-06 02:06:52Z

8

You need to be using list.toArray(new String[list.size()]). An Object[] is not type compatible with String[], despite every element in the Object[] being a String. Also, you should consider specifying the type parameter of your List to maintain type safety.

answered Mar 6, 2012 at 2:06

Jeffrey

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2 Comments

user975044 Over a year ago

I get: The requested resource () is not available. mmm i wonder if something else is wrong then

Jeffrey Over a year ago

@user975044 Without seeing more of your code or the full error message, I can only assume something else is wrong.

S.P. · Accepted Answer · 2012-03-06 02:08:03Z

0

Basically you need to use

String profArr = list.toArray( < String array > (size))

answered Mar 6, 2012 at 2:08

S.P.

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2 Comments

Adam Mihalcin Over a year ago

This code won't even compile. list.toArray returns an array, not a String.

S.P. Over a year ago

I meant this one which seems to have already been provided as an answer list.toArray( new String[list.size]) where in my case <String array is basically any string object array and its size definition>

smart lph · Accepted Answer · 2022-03-03 06:06:34Z

0

you can use java collector

List<Tuple2<String, Boolean>> paras_check
String miss_params= paras_check.stream().map(e->e._1)
            .reduce(",",(x,y)->(x+y));

answered Mar 3, 2022 at 6:06

smart lph

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