when using a array of strings in java, convert it to lowercase

arraylist.stream().map(s -> s.toLowerCase()).collect(Collectors.toList()) 

may help you

If you want a short example, you could do the following

String[] array = ...
String asString = Arrays.toString(array);
if(asString.equals(asString.toLowerCase())
   // no upper case characters.

String  array[]= {"some values"};

String str= String.join(',',array);

String array_uppercase[]=str.toLowerCase().split(',');