CODEWITHSUNDEEP
javaarraysstringdouble
Tarun Zachariah
Tarun Zachariah

Reputation: 15

Adding double values to array list from strings

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!

Upvotes: 1

Views: 2586

Answers (5)

SilentKnight
SilentKnight

Reputation: 14011

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;
}

Upvotes: -2

Epicblood
Epicblood

Reputation: 1177

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));
}

Upvotes: 0

Hailey
Hailey

Reputation: 318

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;
}

Upvotes: 1

Jeffrey Lai Guo Zin
Jeffrey Lai Guo Zin

Reputation: 9

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;
}

Upvotes: 0

Elliott Frisch
Elliott Frisch

Reputation: 201409

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;
}

Upvotes: 2

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