Selecting random key and value sets from a Map in Java

Question

I want to get random keys and their respective values from a Map. The idea is that a random generator would pick a key and display that value. The tricky part is that both k

Answer 1

I would copy the Map into an array and select the entry you want at random. This avoid the need to also lookup the value from the key.

Map x = new HashMap();
Map.Entry[] entries = x.entrySet().toArray(new Map.Entry[0]);
Random rand = new Random();

// call repeatedly
Map.Entry keyValue = entries[rand.nextInt(entries.length)];

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If you want to avoid duplication, you can randomize the order of the entries

Map x = new HashMap();
List> entries = new ArrayList> (x.entrySet());
Collections.shuffle(entries);
for (Map.Entry entry : entries) {
    System.out.println(entry);
}