Question

What is the best way to do this?
Let’s say I have a string that is mixed with letters and numbers,

Srting str = "ha2iwea435";
String str2 = (str Digits);

and I want a string with just the numbers from in between the other letters, or at the end. So my other string would equal the 4th char of str, 2. I suppose I would need to put this in a for loop, and then append a List with the value of str2 so I could assign str2 to 435.
for example,

for(int i = 0; str.length() > i; i++){
    str2 = "";
    if(str(char_here(i).isNUMBER()) {
        for(y = i; str(char_here[y]).isNUMBER(); y++) {
          str2 += str.(char_here);
        }
    }
    List1.add(str2);
}

I have no idea what methods and tests to use.
So in the end, I would have a List that equals (“2”, “435”)

Thanks!

Answer 1

You can use a regex to remove the non-digits characters:

String str = "ha2iwea435";
String numbers = str.replaceAll("[^\\d]","");
System.out.println("numbers = " + numbers); //prints 2435

If you need each group of numbers in a list you can split on letters and add each group to a list:

String str = "ha2iwea435";
String[] numbers = str.split("[^\\d]");

List<Integer> list = new ArrayList<> ();
for (String number : numbers) {
    if (!number.isEmpty()) list.add(Integer.parseInt(number));
}
System.out.println("numbers = " + list); // numbers = [2, 435]

And if you want to store the numbers as Strings:

String str = "ha2iwea435";
String[] numbers = str.split("[^\\d]");

List<String> list = new ArrayList<> (Arrays.asList(numbers));
list.removeAll(Arrays.asList(""));
System.out.println("numbers = " + list); // numbers = [2, 435]