1Z0-829 Java I/O API and Securing Applications — Timed 10 Questions

Question 1

A Java application writes sensitive user data to a file. To ensure that data is not left in the file system after the application crashes, which practice should be followed?

Accepted Answer

Write to a temporary file, then use Files.move() with ATOMIC_MOVE to replace the target file. Writing to a temporary file and then atomically moving it with `Files.move()` using the `ATOMIC_MOVE` option ensures that the target file is replaced only after the write succeeds. If the application crashes during the write, only the temporary file is corrupted, and the original target file remains intact. This prevents sensitive data from being left in an incomplete or partially written state in the file system.

Answer

Call flush() after every write operation

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Delete the file manually in a finally block

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Use a FileLock to prevent concurrent access

Question 2

A Java application running in a secure environment needs to read a file located outside the application's directory. Which approach correctly handles security?

Accepted Answer

Grant java.io.FilePermission in the security policy file for the specific file path. In a secure Java environment, the SecurityManager enforces access controls based on the security policy file. To read a file outside the application's directory, you must explicitly grant `java.io.FilePermission` with the specific file path and the `read` action in the policy file. Without this permission, any attempt to read the file will throw a `java.security.AccessControlException`.

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Use FileInputStream without any additional configuration

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Use java.net.URL to access the file via file:// protocol

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Set the file readable flag using File.setReadable(true)

Question 3

Which TWO statements are true about securing a Java application?

Accepted Answer

A security policy file can grant specific permissions to code from a particular codebase.. A Java security policy file can use a codebase URL (e.g., `codeBase "file:/path/to/jar"`) to grant specific permissions, such as `java.io.FilePermission`, to code loaded from that location. This is a core feature of the Java security model, allowing fine-grained access control based on where the code originates.

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Enabling the security manager is required for all Java applications.

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The Java Cryptography Extension (JCE) is deprecated and should not be used.

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Using code signing guarantees that the application is secure.

Question 4

Which TWO are true about the try-with-resources statement?

Accepted Answer

Resources declared outside the try block can be used if they are effectively final.. The try-with-resources statement allows resources declared outside the try block to be used, provided they are effectively final (i.e., their reference does not change after initialization). This was introduced in Java 9, which enhanced try-with-resources to support effectively final variables in addition to those declared directly within the try parentheses.

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All resources must be of the same type.

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Multiple resources must be separated by commas.

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The resource must implement the Closeable interface.

Question 5

A Java application reads configuration from a file using FileInputStream. The application must handle the case where the configuration file is missing by logging a warning and using default values. Which design approach best meets this requirement?

Accepted Answer

Use Files.exists() to check file existence before opening the stream, and if absent, log a warning and use defaults.. It explicitly checks for file existence using `Files.exists()` before attempting to open the stream, allowing the application to log a warning and fall back to default values without throwing an exception. This approach aligns with the requirement to handle a missing configuration file gracefully, avoiding unnecessary exception handling overhead. The `Files.exists()` method is part of the modern `java.nio.file` API, which is preferred over the legacy `File.exists()` for its better integration with symbolic links and file system operations.

Answer

Wrap the FileInputStream in a try-with-resources and catch Exception to handle missing file.

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Catch FileNotFoundException inside the try block and set default values.

Answer

Use File.exists() to check file existence before opening the stream, and if absent, log a warning and use defaults.

Question 6

Which TWO statements about java.io and java.nio.file packages are true?

Accepted Answer

java.nio.file.Files class provides methods for operating on symbolic links.. Option B is correct because java.nio.file.Files provides static methods that specifically handle symbolic links, such as createSymbolicLink, readSymbolicLink, isSymbolicLink, and delete, which follow or do not follow links as needed. Option C is correct because java.io.RandomAccessFile implements both DataInput and DataOutput and exposes read()/write() methods along with a file pointer (seek, getFilePointer), so it supports both reading from and writing to the same file. Option A is not correct as stated because java.io.Console is obtained via System.console() and reads/writes through its own reader()/writer() tied to the console, not by directly operating on the standard streams System.in/System.out/System.err. Option D is not correct because java.io.FileInputStream does not support mark/reset; markSupported() returns false, unlike BufferedInputStream. Option E is not correct because java.nio.file.Path is an interface, not a class, implemented by platform-specific classes such as sun.nio.fs.UnixPath.

Answer

java.io.Console can be used to read from and write to the standard streams of the JVM.

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java.io.FileInputStream supports the mark and reset methods.

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java.nio.file.Path is a class that represents a file path.

Question 7

Order the steps to create an immutable class in Java.

Accepted Answer

Step 1: Declare the class as final. Step 2: Declare all fields as private and final. Step 3: Provide a constructor that initializes all fields (with defensive copying for mutable fields). Step 4: Do not define any setter methods.. Immutability requires no way to change object state after construction. Defensive copying prevents internal state from being altered.

Answer

Step 1: Declare all fields as private and final. Step 2: Provide a constructor that initializes all fields. Step 3: Declare the class as final. Step 4: Do not define any setter methods.

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Step 1: Provide a constructor that initializes all fields. Step 2: Declare all fields as private and final. Step 3: Declare the class as final. Step 4: Do not define any setter methods.

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Step 1: Do not define any setter methods. Step 2: Declare the class as final. Step 3: Declare all fields as private and final. Step 4: Provide a constructor that initializes all fields.

Question 8

Match each concurrency utility to its purpose.

Accepted Answer

CountDownLatch: A synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes.. This question tests understanding of common concurrency utilities in java.util.concurrent such as CountDownLatch, CyclicBarrier, Semaphore, and Exchanger. A common mistake is confusing CountDownLatch (one-time use) with CyclicBarrier (reusable) and mixing up Semaphore's permit-based control with barrier synchronization.

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CyclicBarrier: A synchronization aid that allows one or more threads to wait until a set of operations completes.

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Semaphore: A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point.

Question 9

A developer needs to read all lines from a text file named "data.txt" that uses UTF-8 encoding. Which code correctly reads the file using the NIO.2 API?

Accepted Answer

Files.readAllLines(Path.of("data.txt"), StandardCharsets.UTF_8). `Files.readAllLines()` reads all lines from a file into a `List<String>`, and it accepts a `Path` and a `Charset` (here `StandardCharsets.UTF_8`) to handle encoding. This method is part of the NIO.2 API and directly fulfills the requirement to read all lines from a UTF-8 encoded file.

Answer

Files.lines(Path.of("data.txt"), StandardCharsets.UTF_8).collect(Collectors.toList())

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Files.readString(Path.of("data.txt"), StandardCharsets.UTF_8)

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Files.readAllBytes(Path.of("data.txt")).toString()