Lecture 2 of Java Programming (with Passion)

[Angela Chung]

Hi Sang,

 

I encountered two questions when I was working on the lecture 2 materials of the course.

 

1) The two classes BufferedReader & JOptionPane

 

I noticed that these two classes are used in different ways in the two example programs.  A new instance is created before BufferedReader method is employed.   It is illustrated as follows:

 

BufferedReader dataIn = new BufferedReader(new InputStreamReader( System.in) );

String name = dataIn.readLine(); // readLine method is called from the instance of BufferedReader.

 

However, in the example of JOptionPane, it is written as ths:

 

String name=JOptionPane.showInputDialog("Please enter your name");

// No instance is created.  Method showInputDialog is called directly from the class JOptionPane.

 

So my question is why are they different?  What is an instance is not created in JOptionPane's case?

 

2) In the lab of "Getting input from keyboard", there is one extra line in the JOptionPane example:

 

public class InputFromKeyboardJOptionPane {

     

    /** Creates a new instance of InputFromKeyboardJOptionPane */

    public InputFromKeyboardJOptionPane() {

    }

     

What is the purpose of creating this self instance of InputFromKeyboardJOptionPane?  It is not explained in the lecture pdf note.

 

Thanks in advance.

Cheers,

Angela