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Java: Dialog Box Input-Output

This is similar to the previous program, but it also gets input from the user.

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// Description: This program gets a string from a dialog box.
// File:   dialogInputOutput/ThirdProgram.java
// Author: Michael Maus
// Date:   29 Jan 2005

import javax.swing.*;

public class ThirdProgram {

    public static void main(String[] args) {
        String humanName;  // A local variable to hold the name.

        humanName = JOptionPane.showInputDialog(null, "What's your name, Earthling");

        JOptionPane.showMessageDialog(null, "Take me to your leader, " + humanName);

        System.exit(0);  // Stop GUI program
    }

}

Line 11 - Declaring a local variable.

This tells the compiler to reserve some memory to hold a String. It's going to hold a name, so we called the variable (a place in the computer's memory) "humanName". The syntax for a simple declaration is to write the type of thing that a variable will hold (String in this case), followed by the variable name (humanName in this case).

Line 13 - Asking the user for a String.

JOptionPane's showInputDialog method displays a message in a dialog box that also accepts user input. It returns a string that can be stored into a variable. This is an assignment statement. The part to the right of the "=" must produce a value, and this value is then stored in the variable on the left (humanName).

Line 15 - Putting two strings together (concatenation)

Concantenation, indicated by the plus sign (+), puts two strings together to build a bigger string, which is then passed as a parameter. The plus sign (+) is also used for addition of numbers.