Map and join elements using Java 8 Streams

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List<String> strings = Arrays.asList("A", "bbb", "CC", "dd");["A","bbb","CC","dd"]
 
// Map the strings to UPPERCASE and join them with the : separator
String joined = strings.stream()
        .map(String::toUpperCase)
        .collect(Collectors.joining(":"));"A:BBB:CC:DD"