Thread: Auto Select

If it's an instance of JTextField, why cast it at all? (Maybe I'm wrong here.)

You're selecting all the text, but it appears you're doing nothing with it.

Anyway, you can set the background color by t.setBackground(Color.Whatever);

I found a class to Highlight.

As for automatically doing it, maybe one of these classes will help.
Java 2 Platform SE v1.3.1: Class DefaultHighlighter
If not, you could always have like an invisible component, a JButton or something like that and give it a Listener and tell it to like button.doClick() or item.setSelected(), or something like that.

Edit: Ok. I guess the if loop is to keep it from casting something that's not a JTextField. Keep the cast.
Anyway, I've always wondered how to get a Highlighter to work myself.

"Create an AutoSelect class at the end of this StudentsScoresApp class that highlights all of the data in the scoreTextField when the mouse is clicked on that TextField. That way, the user doesn’t have to manually highlight the preceding score just to enter a new score."

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.*;
import java.lang.Math;
 
public class StudentScoresApp	{
    public static void main(String[] args)	    {
 
		System.out.println("  List of Student Scores Entered");
        JFrame frame = new StudentScoresFrame();
        frame.setVisible(true);
    }
}
 
class StudentScoresFrame extends JFrame		{
    public StudentScoresFrame()		{
        setTitle("Test Scores");
        setSize(250, 250);
        centerWindow(this);
        setResizable(false);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new StudentScoresPanel();
        this.add(panel);
    }
private void centerWindow(Window w) {
	Toolkit tk = Toolkit.getDefaultToolkit();
	Dimension d = tk.getScreenSize();
	setLocation((d.width-w.getWidth())/2, (d.height-w.getHeight())/2);
	}
}
 
class StudentScoresPanel extends JPanel implements ActionListener	{
    private JTextField  scoreTextField,
                        countTextField,
                        averageTextField,
                        bestTextField,
                        lowestTextField;
    private JLabel      scoreLabel,
                        countLabel,
                        averageLabel,
                        bestLabel,
                        lowestLabel;
    private JButton     enterScoreButton,
    					clearButton,
                        exitButton;
 
	private int count = 0;
 
	private double total = 0;
 
	// total is a double to prevent truncation when
	// calculating the average
	private double average = 0;
	private int best = 0;
	private int lowest = 100;
 
    public StudentScoresPanel()	   {
        // display panel
        JPanel displayPanel = new JPanel();
        displayPanel.setLayout(new FlowLayout(FlowLayout.RIGHT));
 
 
        // score label
        scoreLabel = new JLabel("Test score:");
        displayPanel.add(scoreLabel);
 
        // score text field
        scoreTextField = new JTextField(10);
        displayPanel.add(scoreTextField);
        scoreTextField.requestFocus();
        scoreTextField.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				scoreTextField.selectAll();
			}
		});
 
        // count label
        countLabel = new JLabel("Number of scores:");
        displayPanel.add(countLabel);
 
        // count text field
        countTextField = new JTextField(10);
        countTextField.setEditable(false);
        countTextField.setFocusable(false);
        displayPanel.add(countTextField);
 
        // average label
        averageLabel = new JLabel("Average score:");
        displayPanel.add(averageLabel);
 
        // average text field
        averageTextField = new JTextField(10);
        averageTextField.setEditable(false);
        averageTextField.setFocusable(false);
        displayPanel.add(averageTextField);
 
        // best label
        bestLabel = new JLabel("Highest score:");
        displayPanel.add(bestLabel);
 
        // best text field
        bestTextField = new JTextField(10);
        bestTextField.setEditable(false);
        bestTextField.setFocusable(false);
        displayPanel.add(bestTextField);
 
        // lowest label
        lowestLabel = new JLabel("Lowest score:");
        displayPanel.add(lowestLabel);
 
        // lowest text field
        lowestTextField = new JTextField(10);
        lowestTextField.setEditable(false);
        lowestTextField.setFocusable(false);
        displayPanel.add(lowestTextField);
 
        // button panel
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new FlowLayout(FlowLayout.RIGHT));
 
        // enter score button
        enterScoreButton = new JButton("Enter Score");
        enterScoreButton.addActionListener(this);
        buttonPanel.add(enterScoreButton);
 
        // clear button
        clearButton = new JButton("Clear");
        clearButton.addActionListener(this);
        buttonPanel.add(clearButton);
 
        // exit button
        exitButton = new JButton("Exit");
        exitButton.addActionListener(this);
        buttonPanel.add(exitButton);
 
        // add panels to main panel
        this.setLayout(new BorderLayout());
        this.add(displayPanel, BorderLayout.CENTER);
        this.add(buttonPanel, BorderLayout.SOUTH);
    }
 
 
    public void actionPerformed(ActionEvent e)	{
        Object source = e.getSource();
        if (source == exitButton){
        	if (count == 0){
				lowest = 0;}
 
			NumberFormat ef = NumberFormat.getNumberInstance();
            ef = new DecimalFormat("###.00");
			System.out.println("\n  Highest: " + best + "  Lowest: " + lowest + "  Average: " + ef.format(average) + "\n");
 
				System.out.printf("  Program terminated by the User.");
 
            System.exit(0);
		}
      else if (source == enterScoreButton)	{
            // parse the score
            int score = Integer.parseInt(scoreTextField.getText());
			// calculate the results
            total += score;
            count++;
            average = total / count;
            if (score > best)
            	best = score;
 
            if (score < lowest)
            	lowest = score;
 
			NumberFormat df = NumberFormat.getNumberInstance();
            NumberFormat nf = NumberFormat.getNumberInstance();
            df = new DecimalFormat("###.00");
            countTextField.setText(nf.format(count));
            averageTextField.setText(df.format(average));
            bestTextField.setText(nf.format(best));
            lowestTextField.setText(nf.format(lowest));
            System.out.println("  " + nf.format(count) + ". " + score);
			scoreTextField.selectAll();
        }
        else if (source == clearButton)		{
			if (count == 0)
				lowest = 0;
			NumberFormat df = NumberFormat.getNumberInstance();
            df = new DecimalFormat("###.00");
			System.out.println("\n  Highest: " + best + "  Lowest: " + lowest + "  Average: " + df.format(average) + "\n");
			System.out.println("  Scores were cleared...\n  Next Set:");
			count = 0;
			total = 0;
			average = 0;
			best = 0;
			lowest = 0;
 
            scoreTextField.setText("");
			countTextField.setText("");
            averageTextField.setText("");
            bestTextField.setText("");
            lowestTextField.setText("");
		}
    }
}

I've tried that. I think the focus listener doesn't have what i'm looking for.

::Edit::

I think all I need to do is know how to pass to this now:

 class AutoSelect extends  MouseAdapter {
	public void mouseClicked(MouseEvent e)
			{
				if (e.getComponent() instanceof JTextField)
				{
					JTextField t = (JTextField) e.getComponent();
					t.selectAll();
				}
			}
	}

i can't seem to figure out how to because I don't knwo how to pass to it and also where in my code to do so.

I just need it to auto select all the text in the JTextfield once the box is clicked once, instead of the user having to highlight it all them selves and delete it.