TGTestingStringsList.java

  // First, let's declare a list of Strings, 
  // using the previous String variables:
  String[] stringsToConcat = 
    new String[]{singleSpaceString, nullString, notEmptyString};
  
  // Now we can use a join method to concatenate the variables:
  String joinedText = String.join(stringsToConcat, '');

  // This is the result:
  |DEBUG|concatenated joinedText:  Samwise Gamgee is the real hero
  
  // Note the null value was not added to String this time.
  // Let's concatenate only the null and empty strings: 
  stringsToConcat = new String[]{singleSpaceString, nullString};
  joinedText = String.join(stringsToConcat, '');

  // Now, the interesting part: 
  // let's find out if this variable is Empty or Null:
  Boolean isBlank = String.isBlank(joinedText);
  Boolean isEmpty = String.isEmpty(joinedText);

  |DEBUG|concatenated isBlank: true
  |DEBUG|concatenated isEmpty: false