//IntCheck.java
//howto input an int without program-terminating error
//1. via a JTextField
//2. via JOptionPane
//try catch blocks used

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class IntCheck implements ActionListener {

    JFrame outputFrame;
    Container container;
    JLabel intLabel;
    JTextField intTextField;
    JButton interactiveButton;
    JLabel goodIntLabel;

    public static void main(String[] args) {

	IntCheck demoIntCheck = new IntCheck();   //create object of this class
    }

    //constructor
    public IntCheck() {
        outputFrame = new JFrame();
        outputFrame.setSize(800,300);
        outputFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        container = outputFrame.getContentPane();  
        container.setLayout( new FlowLayout() );

	intLabel = new JLabel("Enter an integer:");
	container.add(intLabel);

	intTextField = new JTextField( "", 10 ); 
        container.add( intTextField );
        intTextField.addActionListener( this ); 

        interactiveButton = new JButton( "use JOptionPane" );
        container.add( interactiveButton );
        interactiveButton.addActionListener( this ); 

	goodIntLabel = new JLabel("integer is: ");   //will include int value
	container.add(goodIntLabel);

       outputFrame.setVisible(true);
    }

    
    public void actionPerformed( ActionEvent event ) {
	int num;

        if ( event.getSource() == intTextField ) {
	    //test the text in the textfield to see if it is integer
	    try {
		num = Integer.parseInt( intTextField.getText() );
		//happens if no parseInt error:
		goodIntLabel.setText("good int: " + num);    //and could now use the int...
	    } catch (NumberFormatException e) {
		//happens if parseInt error:
		goodIntLabel.setText("bad attempt: " + intTextField.getText());
	    }
        }
        else if ( event.getSource() == interactiveButton ) {
	    num = getInt();  //interactively using JOptionPane get int 
	    goodIntLabel.setText("good int: " + num);
	    //and could now use the int...
	}
    }

    //JOptionPane dialog box interactively input an int without runtime exception
    public int getInt() {
	String input;
	int num=0;   //initialize to fake out compiler
	boolean goodInt;

	goodInt = false;    //not gotten good int yet
	do {
	    try {
		input = JOptionPane.showInputDialog( "Enter an integer" );
		num = Integer.parseInt( input );
		goodInt = true;  //if get this far, is a good int
	    } catch (NumberFormatException e) {
		//some message to user:
		//System.out.println("oops, do you really mean that?"); 
		JOptionPane.showMessageDialog(null, "Invalid integer.  Try again");
	    }
	} while (!goodInt);

	return num;
    }
}