Programming Practice

Method:public static char[] firstChars(String[] arr)

Creates an array containing the first character of each entry in an array of Strings. If arr is null, returns null. Otherwise, it returns an array containing the first letter of each entry in arr. If an entry of arr is null or empty, the corresponding entry in the output should be ?. For example firstChars({"hello","world",null,"lol","","yolo"}) should return ['h','w','?','l','?','y'].

Parameters: arr The input array.

Returns: An array containing the first character of each entry in arr if arr is not null, or null if arr is null.