JOptionPane

Question

JOptionPane.showMessageDialog(null,"the sum is "+sum,"Answer",JOptionPane.PLAIN_MESSAGE);
// what is the meaning of "JOptionPane.PLAIN_MESSAGE"? is it a kind of object?

Answer 1

Good question. PLAIN_MESSAGE is a static variable of JOptionPane class. Static variables are variables belonging to a class rather than an object. They can be called directly on the class.

In this case PLAIN_MESSAGE holds an integer value which indicates to the showMessageDialog that the dialog is a plain message.

Answer 2

it is the constant with meaning: "No icon is used".

public static final int PLAIN_MESSAGE