检查用户输入的数字java的格式

Question

I want to check whether the user entered double value is in the format XXX.YYY. If it is then it would return true otherwise false. I want to know if its possible to do this with decimalFormat class. People have said to use regex, but that is out of scope for me right now.

Answer 1

Pure java string solution:

  public static boolean isValid(String str) {
    if (str == null || str.length() != 7) {
      return false;
    }
    return Character.isDigit(str.charAt(0)) && Character.isDigit(str.charAt(1)) && Character.isDigit(str.charAt(2))
      && str.charAt(3)=='.' && 
      Character.isDigit(str.charAt(4)) && Character.isDigit(str.charAt(5)) && Character.isDigit(str.charAt(6));
  }

  public static void main(String[] args) {
    System.out.println(isValid("123.456"));
    System.out.println(isValid("12.456"));
    System.out.println(isValid("abc.456"));
  }

Answer 2

try this

    String s = new String("123.456"); // suppose it is string from your file
    String[] splitted  = s.split("\\."); //take the part before and after do in the array , splitted is array of two strings
    if(splitted.lenght == 2 && splitted[0].length() == 3 && splitted[1].length() == 3) // then it is in abc.xyz format