Identify the Key-Value pair having duplicate values

Question

I have a multimap like below:

{20014=[13123], 20013=[45451, 13123]}

where the keys and values are in String

If there is any duplicate in the value from other key, I have to print that key-value pair. In this case, it will be Key-20013,Value-13123.

How to achieve this? I checked this link but not getting how to get the duplicate pair.

Answer 1

It could be done like this:

// Initialize my multimap
Multimap<String, String> multimap = ArrayListMultimap.create();
multimap.put("20014", "13123");
multimap.put("20013", "45451");
multimap.put("20013", "13123");

// Set in which we store the values to know if they exist already
Set<String> allValues = new HashSet<>();
// Convert the multimap into a Map
Map<String, Collection<String>> map = multimap.asMap();
// Iterate over the existing entries
for (Map.Entry<String, Collection<String>> entry : map.entrySet()) {
    String key = entry.getKey();
    Collection<String> values =  entry.getValue();
    // Iterate over the existing values for a given key
    for (String value : values) {
        // Check if the value has already been defined if so print a log message
        if (!allValues.add(value)) {
            System.out.println(String.format("Key-%s,Value-%s", key, value));
        }
    }
}

Output:

Key-20013,Value-13123