如何在字符串中的项目之间添加空格

Question

How can I add a space between distinct items in a string. Given the string for example:

"22@((12@45)&14)"

How can I make it a string separated by spaces like this:

"22 @ ( ( 12 @ 45 ) & 14 )"

Note that numbers greater than 9 don't have a space in between their digits

Answer 1

You can try with this, it works, and it will give you a base for modifications if you need them:

public static void main(String[] args) {
    String someString = "22@((12@45)&14)";
    int length = someString.length();
    StringBuilder result = new StringBuilder();
    for (int i = 0; i < length; i++) {
        char c = someString.charAt(i);
        result.append(c);
        if (!Character.isDigit(c) || (i < length-1 && !Character.isDigit(someString.charAt(i+1)))){
            result.append(" ");
        }
    }
    System.out.println(result.toString());
}

Answer 2

If you have only integer numbers, it can be implemented as following:

        private static String formatExpression(String input) {
            return String.join(" ", input.split("((?<=\\D)|(?=\\D))"));
        }

1. Splitting by non-digits using lookahead/lookbehind syntax;
2. Rejoining to String using space delimiter.