public static void main(String[] args) {

List<String> list = Arrays.asList("apple", "banana", "cherry", "date", "1","2");

Map<Integer, String> map = list.stream()

.collect(Collectors.toMap(

String::length, // Key is the length of the string

str -> str, // Value is the string itself

(existing, replacement) -> {

System.out.println("Duplicate key detected: " + existing + " and " + replacement);

return existing; // Keep the existing value

}));

System.out.println(map);

// To return both existing & replacement

// Create a Map where the key is the string length and the value is a List of

// Strings

Map<Integer, List<String>> mapforExistingReplacement = list.stream()

.collect(Collectors.toMap(

String::length, // Key is the length of the string

str -> new ArrayList<>(Collections.singletonList(str)), // Initialize with the first value in a

// list

(existing, replacement) -> {

existing.addAll(replacement); // Add the replacement to the existing list

return existing; // Return the updated list

}));

// Map<Integer, String> map = list.stream()

// .collect(Collectors.toMap(String::length, str -> str));

System.out.println(mapforExistingReplacement);

// Using a Set for Unique Values

// If you want to avoid duplicates and store each value only once, you can use a

// Set instead of a List. A Set will automatically handle duplicate entries.

// Create a Map where the key is the string length and the value is a Set of Strings

Map<Integer, Set<String>> mapToSetMap = list.stream()

.collect(Collectors.toMap(

String::length, // Key is the length of the string

str -> new HashSet<>(Collections.singletonList(str)), // Initialize with the first value in a Set

(existing, replacement) -> {

existing.addAll(replacement); // Add the replacement to the existing Set

return existing; // Return the updated Set

}

));

System.out.println("maptoSetMap " +mapToSetMap);

//map to list

Map<Integer, List<String>> mapToList = list.stream()

.collect(Collectors.groupingBy(

String::length, // Key is the length of the string

Collectors.toList() // Value is a List of strings

));

System.out.println("mapToList " + mapToList);

}