import java.util.concurrent.ConcurrentHashMap;
public class Main {
public static void main(String[] args) {
ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();
for (int i = 0; i < 10; i++) {
final int index = i;
new Thread(() -> {
for (int j = 0; j < 100; j++) {
map.put("Key" + index, map.getOrDefault("Key" + index, 0) + 1);
}
}).start();
}
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
for (String key : map.keySet()) {
System.out.println(key + ": " + map.get(key));
}
}
}
