import java.util.HashMap;

import java.util.Map;

import java.util.concurrent.TimeUnit;

public class TimestampCache {

private final Map<String, Long> cache = new HashMap<>();

private final long cacheDuration;

public TimestampCache(long cacheDuration) {

this.cacheDuration = cacheDuration;

}

public long getTimestamp(String key) {

// Check if the timestamp is in the cache

if (cache.containsKey(key)) {

long timestamp = cache.get(key);

// Check if the timestamp is still valid

if (System.currentTimeMillis() - timestamp < cacheDuration) {

return timestamp; // Return cached timestamp

} else {

// Cache expired, remove it

cache.remove(key);

}

}

// If not in cache or expired, get the timestamp from the source

try {

return getTimestampFromSource(key);

} catch (Exception e) {

// Handle failure gracefully (e.g., log the error, return a default value)

System.err.println("Error fetching timestamp for key " + key + ": " + e.getMessage());

return -1; // Or another default value indicating failure

}

}

private long getTimestampFromSource(String key) throws Exception {

// Simulate fetching a timestamp from a source (e.g., a database, API)

// Replace this with your actual timestamp retrieval logic

System.out.println("Fetching timestamp from source for key: " + key);

return System.currentTimeMillis();

}

public void setTimestamp(String key, long timestamp) {

cache.put(key, timestamp); // Store timestamp in cache

}

public static void main(String[] args) throws Exception {

TimestampCache cache = new TimestampCache(10, TimeUnit.SECONDS);

// Example usage

long timestamp1 = cache.getTimestamp("key1");

System.out.println("Timestamp for key1: " + timestamp1);

long timestamp2 = cache.getTimestamp("key1"); // Should be from cache if within duration

System.out.println("Timestamp for key1 (again): " + timestamp2);

long timestamp3 = cache.getTimestamp("key2"); // New key, fetch from source

System.out.println("Timestamp for key2: " + timestamp3);

// Simulate fetching from source

cache.setTimestamp("key1", System.currentTimeMillis());

long timestamp4 = cache.getTimestamp("key1");

System.out.println("Timestamp for key1 (after set): " + timestamp4);

Thread.sleep(11000); // Wait for cache to expire

long timestamp5 = cache.getTimestamp("key1"); // Should fetch from source again

System.out.println("Timestamp for key1 (after expiration): " + timestamp5);

}

}