Adding double values to array list from strings

Question

I'm trying to covert an array of strings into an array of doubles. I'm fairly familiar with ArrayList<>() , but i see there is in an example code give, double[].

example: list = ["1" , "2" , "3"] desired return: number = [1 , 2 , 3]

public double[] ConversionNumber
{
double[] sequence = new double[list.size()];
for(String element:list){
double val = Double.parseDouble(element);
sequence.add(val)}

return sequence;

when i do this, i get an error in Bluej compiler: "cannot find symbol- method add(double).

What is a good way to solve this (i'm a beginner at Java).

thanks!

i created list using: ArrayList<String> list = new ArrayList<String>() — Tarun Zachariah
– Tarun Zachariah, Commented Apr 8, 2015 at 2:13

Elliott Frisch · Accepted Answer · 2015-04-08 01:44:42Z

2

If list is an array, then list.size() would fail. I think we can assume it should be a List<String>. And you access an array by index. Also, I assume it should be an argument to your method. Next, Java convention for methods names is camelCase.

public double[] conversionNumber(List<String> list) {
    double[] sequence = new double[list.size()];
    int pos = 0;
    for (String element : list) {
        double val = Double.parseDouble(element);
        sequence[pos++] = val; // <-- post-increment
    }
    return sequence;
}

answered Apr 8, 2015 at 1:44

Elliott Frisch

202k20 gold badges166 silver badges265 bronze badges

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

2 Comments

Kon Over a year ago

The problem is he's calling add on an array, not the list.size() call based on his error

Epicblood Over a year ago

im assuming that because he wants a double[], list is probably a String[] not a List

Hailey · Accepted Answer · 2015-04-08 01:57:54Z

1

Generally, if you're working with Collections, you work with collections the whole way. It's bad form to use Lists for one thing, but arrays for another. So it's advisable to do this with a List<Double> instead of a double[]

public List<Double> parseDoubles(List<String> strings) {
    List<Double> doubles = new ArrayList<>(strings.size());
    for(String string : strings) {
        doubles.add(new Double(string));
    }
    return doubles;
}

answered Apr 8, 2015 at 1:57

Hailey

3181 silver badge6 bronze badges

Comments

Jeffrey Lai Guo Zin · Accepted Answer · 2015-04-08 01:47:57Z

0

Below code will work for your case:

java.util.List<String> list = java.util.Arrays.asList("1", "2", "3");
public double[] ConversionNumber() {
    double[] sequence = new double[list.size()];
    int i = 0;
    for(String element:list){
        double val = Double.parseDouble(element);
        sequence[++i] = val;
    }
    return sequence;
}

answered Apr 8, 2015 at 1:47

Jeffrey Lai Guo Zin

91 bronze badge

Comments

Epicblood · Accepted Answer · 2015-04-09 01:28:47Z

0

The error happens because arrays dont have an 'add' method. You will want to do something like:

double[] sequence = new double[list.length]; 
for(int i = 0; i < list.length; i++){
    sequence[i] = Double.parseDouble(list[i]);
}

If list is an actual List not a String[] as I assumed, you would do:

double[] sequence = new double[list.size()]; 
for(int i = 0; i < list.size(); i++){
    sequence[i] = Double.parseDouble(list.get(i));
}

edited Apr 9, 2015 at 1:28

answered Apr 8, 2015 at 1:45

Epicblood

1,1772 gold badges10 silver badges29 bronze badges

1 Comment

SilentKnight Over a year ago

new double[list.length -1], the size of the double[] is not right here.

Epicblood · Accepted Answer · 2015-04-09 01:42:18Z

-2

Change your code here

for(String element:list){
    double val = Double.parseDouble(element);
    sequence.add(val)
}

to this if your list is a List:

for(int i=0;i<list.size();i++){
    double val = Double.parseDouble(list.get(i));
    sequence[i]=val;
}

if your list is an Array, then change to this:

for(int i=0;i<list.length;i++){
    double val = Double.parseDouble(list[i]);
    sequence[i]=val;
}

edited Apr 9, 2015 at 1:42

Epicblood

1,1772 gold badges10 silver badges29 bronze badges

answered Apr 8, 2015 at 1:46

SilentKnight

14.1k19 gold badges52 silver badges80 bronze badges

4 Comments

Epicblood Over a year ago

arrays don't have a size() method and they don't have a get() method

SilentKnight Over a year ago

@Epicblood Come on, list is a List, don't you see list.size() in his codes? My answer is right absolutely

Epicblood Over a year ago

"I'm trying to covert an array of strings"

Epicblood Over a year ago

Looking at the code it might be a List, however because he wants the results in an array as well, it's safe to assume that list is an array. He tries to call add() on an array, so the size() and get() may be in error as well.

Collectives™ on Stack Overflow

Adding double values to array list from strings

5 Answers 5

2 Comments

Comments

Comments

1 Comment

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

2 Comments

Comments

Comments

1 Comment

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related