Core java interview Questions You'll Most Likely Be Asked (Second Edition)

Explain with a code sample how you can create a
directory on the file system.
Answer:
There is a method called mkdir() on the File class that creates a
directory corresponding to the specified file object. The following
code uses this method to create a directory in the file system:
File myDirectory = new File(“/usr/mydir”); //1
myDirectory.mkdir(); //2
Line 1 creates a file object. Line 2 invokes the mkdir() method
to creates an actual directory.
Explain what happens when the following code is
compiled and executed.
File myDirectory = new File(“/usr/JavaCodes”);

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182.
File myNewFile = new
File(“/usr/JavaCodes/CoreJava.txt”); //line 1
myNewFile.createNewFile();
Answer:
The above code throws an IOException. This is because the
directory /usr/JavaCodes/ is not created, only a file object
myDirectory corresponding to it is created. In order for the code
to work, you need to add the following line of code before Line 1:
myDirectory.mkdir();
Write a code sample that demonstrates the PrintWriter
class.
Answer:
The PrintWriter is a specialization of the Writer class can be
used to write formatted representations of objects. The following
code demonstrates how the PrintWriter can be used to write
a String:
File myNewFile = new File(“/usr/CoreJava.txt”);
PrintWriter myPrintWriter = new PrintWriter(myNewFile);
//Line 1
myPrintWriter.println(“This gets inserted into the
File”); //Line 2
myPrintWriter.close(); //Line 3
In the above code, when Line 1 is executed, the file CoreJava.txt
is created inside the folder /usr/.
When Line 2 is executed, the println() method writes the
String specified in the file CoreJava.txt and terminates the line.

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