1Z0-819 Sample Questions & Answers

A developer is writing a utility method to format currency values for different regions. The method should take a double and a java.util.Locale and return a formatted string. The application will be used in the US, Germany, and Japan. Which is the correct way to instantiate and use a NumberFormat object for this purpose?

Given the following code:

public class Device {
private String type = "electronic";
public String getType() { return type; }
}

public class Phone extends Device {
private String type = "mobile";
@Override
public String getType() { return type; }
}

public class Tester {
public static void main(String[] args) {
Device device = new Phone();
System.out.println(device.type + ":" + device.getType());
}
}

What is the result?

A developer needs to process a list of Order objects. The goal is to create a Map where keys are the Customer associated with the order, and values are a List of all Order objects for that customer. Which stream operation correctly achieves this?

A developer has created a custom annotation @Version to track the version of a class. The annotation must be available at runtime via reflection and should be included in the generated Javadoc.

// line n1
public @interface Version {
String value();
}

Which meta-annotations should be placed at line n1 to meet these requirements? (Select TWO)

A developer is implementing a custom collection class that must be usable in a for-each loop. Which interface must the custom class implement to support this functionality?

What is the output of the following code snippet?

var list = new java.util.ArrayList ();
list.add("A");
list.add("B");
list.add("C");

for (var s : list) {
System.out.print(s);
list.remove(s);
}

A database administrator needs a Java application to connect to an Oracle database. The connection details are: driver oracle.jdbc.driver.OracleDriver, URL jdbc:oracle:thin:@host:1521:sid, user scott, and password tiger. Which code fragment correctly establishes a connection to the database?

A developer is creating an immutable User class. Which of the following principles must be followed to ensure true immutability? (Select THREE)

Case Study

Company Background:
GlobalTrade Inc. is a logistics company that provides real-time tracking for international shipments. They are developing a new backend service, TrackingService, using Java 11. This service receives location updates from various carriers, validates them, and stores them in a database. Performance and reliability are critical, as the service must handle thousands of updates per second.

Current Situation:
The development team has created a LocationUpdateProcessor class that runs in its own thread. This processor fetches batches of raw location data from a shared queue, processes them, and writes them to the database. During initial load testing, the team observed that under heavy load, the application sometimes throws a NullPointerException within the run() method of the processor. The code for the processor is as follows:

class LocationUpdateProcessor implements Runnable {
private volatile boolean isRunning = true;
private final Queue dataQueue;

public LocationUpdateProcessor(Queue queue) { this.dataQueue = queue; }

public void stopProcessing() { isRunning = false; }

@Override
public void run() {
while (isRunning) {
String rawData = dataQueue.poll();
// NPE occurs on the next line
if (rawData.contains("URGENT")) {
// process urgent data
}
}
}
}

Requirements:
The LocationUpdateProcessor must be fixed to prevent the NullPointerException. It should process data as long as the isRunning flag is true and there is data in the queue. The solution must be efficient and avoid busy-waiting (i.e., continuously looping and checking the queue when it's empty).

Question:
Which modification to the run() method is the most appropriate and robust solution to fix the bug and meet the requirements?

What is the purpose of the var keyword introduced in Java 10 and available in Java 11?