如何将A字符串变成double

Question

I have this string called strg "12*2/5-3.0^3.23" i want to turn every int in this string into a double. I've tried a lot of this and nothing is working. i've tried splitting the string everywhere there is a special character and then checking if it is already a double or not by doing something like if(splt[i].contains(".")){isDouble == true;} if it is a double i don't touch it if it wasn't a double i did something like splt[i]=splt[i]+".0"; to change it to a double. I'm fine up to this point but how do i change it back into a string and not a split string.

Answer 1

final class Playground {
  private static List<Double> extract(final String input) {
    final List<Double> results = new LinkedList<>();
    StringBuilder builder = new StringBuilder(1);
    for (final char character : input.toCharArray()) {
      if (Character.isDigit(character) || (Character.compare(character, '.') == 0)) {
        builder.append(character);
      } else {
        results.add(Double.valueOf(builder.toString()));
        builder = new StringBuilder(1);
      }
    }
    if (builder.length() > 0) {
      results.add(Double.valueOf(builder.toString()));
    }
    return results;
  }

  public static void main(final String... args) {
    System.out.printf("[numbers] %s", Playground.extract("12*2/5-3.0^3.23"))
  }
}