OCPJP(SCJP1.6) Question 30

   1: import java.io.File;

   2: import java.io.IOException;

   3:  

   4: /**

   5:  * Created by IntelliJ IDEA.

   6:  * User: Owner

   7:  * Date: 8/6/11

   8:  * Time: 12:57 PM 

   9:  */

  10: public class TestCreateNewFile {

  11:     public static void main(String[] args) throws IOException {

  12:         File f = new File("scjp6exam.txt");

  13:         System.out.println(f.exists());

  14:         f.createNewFile();

  15:         System.out.println(f.exists());

  16:     }

  17: }

Options :

A. Prints “ false, false”.

B. Prints “ false, true”

C. Can throw an exception at Line 14.

D. Line 15 may not be executed.

Answer : B, C, D

 

A is incorrect because after creating a file in line 14 f.exists() returns if the file has been created successfully. However f.createNewFile() can throw an IOException for many reason. One of such could be creating a file in a read-only directory. If the exception is thrown then line 15 does not get executed. So C and D are also correct.

 

File –> createNewFile() Java 1.6 API

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public boolean createNewFile()
                      throws IOException

Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist. The check for the existence of the file and the creation of the file if it does not exist are a single operation that is atomic with respect to all other filesystem activities that might affect the file.

Note: this method should not be used for file-locking, as the resulting protocol cannot be made to work reliably. The FileLock facility should be used instead.

Returns:

true if the named file does not exist and was successfully created; false if the named file already exists

Throws:

IOException - If an I/O error occurred

SecurityException - If a security manager exists and its SecurityManager.checkWrite(java.lang.String) method denies write access to the file

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