import java.util.HashMap;

import java.util.Map;

import java.util.concurrent.Executors;

import java.util.concurrent.ScheduledExecutorService;

import java.util.concurrent.TimeUnit;

public class QueryStringWatcher {

private static final int DEFAULT_RETRY_INTERVAL = 2; // seconds

private final int retryInterval;

private final Map<String, String> lastQueryString;

public QueryStringWatcher(int retryInterval) {

this.retryInterval = retryInterval;

this.lastQueryString = new HashMap<>();

}

public void watchQueryString(String queryString) {

// Store the current query string

lastQueryString.put(queryString);

// Simulate a background task that checks for changes

ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();

scheduler.scheduleAtFixedRate(() -> {

String currentQueryString = getQueryString();

if (!currentQueryString.equals(lastQueryString.get(queryString))) {

System.out.println("Query string changed: " + currentQueryString);

lastQueryString.put(queryString, currentQueryString);

}

}, 0, retryInterval, TimeUnit.SECONDS);

}

private String getQueryString() {

// Placeholder for getting the query string. Replace with your actual implementation.

// This simulates reading from a request object or environment variable.

// Example: Read from System.getProperty("query.string")

String queryString = System.getProperty("query.string");

if (queryString == null) {

queryString = "default"; //Default value if not found

}

return queryString;

}

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

// Example Usage

QueryStringWatcher watcher = new QueryStringWatcher(5); // Retry every 5 seconds

// Simulate changes to the query string

String initialQueryString = "initial=value";

watcher.watchQueryString(initialQueryString);

Thread.sleep(2000); // Wait 2 seconds

watcher.watchQueryString("updated=value"); // Simulate a change

Thread.sleep(2000);

watcher.watchQueryString("updated2=value");

}

}