将字符串ArrayList转换为Double ArrayList

Question

I'm trying to convert my String ArrayList into a Double ArrayList and for some reason it is not converting right.

My input:

1 2 3 4

My output:

[1.0]
[1.0, 1.0, 2.0]
[1.0, 1.0, 2.0, 1.0, 2.0, 3.0]
[1.0, 1.0, 2.0, 1.0, 2.0, 3.0, 1.0, 2.0, 3.0, 4.0]

Expected Output:

[1.0] [1.0, 2.0] [1.0, 2.0, 3.0] [1.0, 2.0, 3.0, 4.0]

My Code

String inputValue;


List<String> input = new ArrayList<String>();
List<Double> numbers = new ArrayList<Double>();



while((inputValue = stdin.readLine()) != null) {

   input.add(inputValue);

    for(int i = 0; i < input.size(); i++) {
        numbers.add (Double.parseDouble(input.get(i)));
    }
    System.out.println(numbers);
}

Answer 1

You don't need two loops - you can convert the String to double when you read the input from stdin . Beside that, the output should be printed after the loop in done, once all the numbers are in the lists :

    while((inputValue = stdin.readLine()) != null){
       input.add(inputValue);
       numbers.add (Double.parseDouble(inputValue));
    } 
    System.out.println(numbers);

Actually, I'm not sure you even need the input list.

EDIT :

If you want to print the input as it is added to the Lists, and handle bad input, as well as allow the user to quit the loop by typing enter (ie an empty line) :

    while((inputValue = stdin.readLine()) != null && !inputValue.isEmpty()) {
       input.add(inputValue);
       try {
           numbers.add (Double.parseDouble(inputValue));
           System.out.println(numbers);
       }
       catch (NumberFormatException numEx) {
           System.out.println(inputValue + " is not a double");
       }
    }