Java SE 8 Programmer II Exam: Question Analysis and Solutions

Modify Code to Print "Open Close" - 1Z0-809 | Oracle Certified Professional

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Question

Given: final class Folder {//line n1 //line n2 public void open () { System.out.print("Open"); } } public class Test { public static void main (String [] args) throws Exception{ try (Folder f = new Folder()){ f.open(); } } } Which two modifications enable the code to print Open Close? (Choose two.)

Answers

A. Replace line n1 with: class Folder implements AutoCloseable {

B. Replace line n1 with: class Folder extends Closeable {

C. Replace line n1 with: class Folder extends Exception {

D. At line n2, insert: final void close () { System.out.print("Close"); }

E. At line n2, insert: public void close () throws IOException { System.out.print("Close"); }

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Explanations

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A. B. C. D. E.

AE.

This code snippet demonstrates the use of try-with-resources statement in Java. The try-with-resources statement is a try statement that declares one or more resources, and ensures that each resource is closed after the statement has completed its execution.

The given code declares a final class Folder which has a method named open(). The main() method instantiates a new Folder object within the try-with-resources statement and then calls the open() method on it.

To enable the code to print "Open Close", we need to modify the given code in two ways:

Implement the AutoCloseable or Closeable interface in the Folder class so that the close() method is automatically called when the try block completes.
Define the close() method in the Folder class to print "Close".

Option A and Option B provide two ways to implement the AutoCloseable or Closeable interface in the Folder class:

Option A: Replace line n1 with class Folder implements AutoCloseable { This modification enables the Folder class to implement the AutoCloseable interface, which requires the implementation of the close() method. The close() method is automatically called by the try-with-resources statement when the try block completes.

Option B: Replace line n1 with class Folder extends Closeable { This modification enables the Folder class to extend the Closeable interface, which also requires the implementation of the close() method. The close() method is automatically called by the try-with-resources statement when the try block completes.

Option C is incorrect because extending the Exception class does not provide the necessary interface or methods for the Folder class to be automatically closed by the try-with-resources statement.

Option D and Option E provide two ways to define the close() method in the Folder class:

Option D: At line n2, insert final void close() { System.out.print("Close"); } This modification defines a close() method in the Folder class that prints "Close" and is called when the try block completes. However, without implementing AutoCloseable or Closeable interface, the close() method will not be automatically called by the try-with-resources statement.

Option E: At line n2, insert public void close() throws IOException { System.out.print("Close"); } This modification defines a close() method in the Folder class that prints "Close" and throws an IOException (which is a checked exception). However, without implementing AutoCloseable or Closeable interface, the close() method will not be automatically called by the try-with-resources statement.

Therefore, the correct options are A and D. After making these two modifications, the code will print "Open Close" when it is executed.

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