如何使用for循环将字符串arraylist转换为double？

Question

I'm given the data.txt file and have to calculate the total amount using ArrayList

my data.txt file contains:

32.14,235.1,341.4,134.41,335.3,132.1,34.1

so far I have

public void processFile() throws IOException
{
    File file = new File("SalesData.txt");

    Scanner input = new Scanner(file);
    ArrayList<String> arr = new ArrayList<String>();
    String line = input.nextLine();

    StringTokenizer st = new StringTokenizer(line, ",");

    while (st.hasMoreTokens())
    {
        arr.add(st.nextToken());
    }

    setArrayListElement(arr); //calls setArrayListElement method

}

and here is my setArrayListElement method:

private void setArrayListElement(ArrayList inArray)
{                
    for (int i = 0 ; i < inArray.size() ; i++)
    {
         // need to convert each string into double and sum them up
    }
}

Can I get some help??

Answer 1

1. Never use doubles for monetary calculations (Previous answer is also wrong)
2. Never refer to a concrete class. The interface in this case is List arr = new ArrayList();

To your specific answer:

BigDecimal summed = BigDecimal.ZERO;

for (int i = 0 ; i < arr.size() ; i++) {
 final String value  = arr.get(i);
 try{
  BigDecimal bd = new BigDecimal(value);
  summed = summed.add(bd);
 } catch(NumberFormatException nfe){
       //TODO: Handle
 }
}

...

Answer 2

您必须使用Double.valueOf() ：

Double.valueOf(string);

Answer 3

Double value = Double.parseDouble(yourString);

Answer 4

I post you the method to calculate the total amount, dont forget to control exceptions.

    private Double setArrayListElement(ArrayList inArray) throws NumberFormatException
{   
    Double amount=0;    
    for (int i = 0 ; i < inArray.size() ; i++)
    {
       amount= amount+Double.valueOf(inArray.get(i));
    }
    return amount;
}