[Algo] 281. Remove Spaces

public class Solution {
  public String removeSpaces(String input) {
    // Write your solution here
    if (input == null || input.length() == 0) {
      return input;
    }
    char[] charArr = input.toCharArray();
    int slow = 0;
    for (int i = 0; i < charArr.length; i++) {
      if (charArr[i] == ‘ ‘ && (i == 0 || charArr[i - 1] == ‘ ‘)) {
        continue;
      }
      charArr[slow++] = charArr[i];
    }
    // slow > 0  for case "    "
    if (slow > 0 && charArr[slow - 1] == ‘ ‘) {
      return new String(charArr, 0, slow - 1);
    }
      return new String(charArr, 0, slow);
  }
}