Text Input Components

TextField

Textfields are single line areas that can be used to enter in data from the keyboard while a program is running. To create a text field use any of the constructors:

TextField()
TextField(int columns) // where columns gives the TextField a width
TextField(String s)
TextField(String s, int columns)

To allow a user to enter a password or any other hidden text use:

setEchoChar(char c)      // normally char c is '*'
boolean echoCharIsSet()

To make the Textfield editable or un-editable use:

setEditable(boolean editable) // true means editable

TextField Example: (Run Applet)

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

public class TextFieldDemo extends JApplet
{
    @Override
    public void init()
    {
        this.setContentPane(new View());
    }

    public class View extends JPanel implements DocumentListener
    {
        private final JTextField text;
        private final JLabel message = new JLabel("");

        public View()
        {
            super();

            this.setLayout(new BorderLayout());

            this.text = new JTextField(20);  // 20 characters wide
            this.add("North", this.text);
            this.add("South", this.message);

            // Add Document listener for the document that is attached
            // to the JTextField
            final Document document = this.text.getDocument();
            document.addDocumentListener(this);

            this.text.requestFocus();
        }

        @Override
        public void insertUpdate(DocumentEvent e)
        {
            showText();
        }

        @Override
        public void removeUpdate(DocumentEvent e)
        {
            showText();
        }

        @Override
        public void changedUpdate(DocumentEvent e)
        {
            showText();
        }

        private void showText()
        {
            this.message.setText("Text input is: " + this.text.getText());
        }
    }
}

Password

Passwords are TextFields that have their text hidden.

PasswordDemo Example: (Run Applet)

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

public class PasswordDemo extends JApplet
{
    @Override
    public void init()
    {
        this.setContentPane(new View());
    }

    public class View extends JPanel implements DocumentListener
    {
        // Password
        private final JPasswordField password = new JPasswordField(20);
        private final JLabel message = new JLabel();

        public View()
        {
            super();
            // add a document listener to the password field
            final Document passwordDocument;
            passwordDocument = this.password.getDocument();
            passwordDocument.addDocumentListener(this);

            // applet Panel layout
            this.setLayout(new BorderLayout());
            this.add("North", this.password);
            this.add("South", this.message);
        }

        // Document Listener overrides
        @Override
        public void insertUpdate(DocumentEvent e)
        {
            showMessage();
        }

        @Override
        public void removeUpdate(DocumentEvent e)
        {
            showMessage();
        }

        @Override
        public void changedUpdate(DocumentEvent e)
        {
            showMessage();
        }

        private void showMessage()
        {
            this.message.setText(new String(this.password.getPassword()));
        }
    }
}

The password echo character can be turned off by setting it to (char)0.

Password_Hint_Demo Example: (Run Applet)

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

public class Password_Hint_Demo extends JApplet
{
    @Override
    public void init()
    {
        this.setContentPane(new View());
    }

    public class View extends JPanel
    {
        private final HintPasswordField password = new HintPasswordField(20);
        private final HintPasswordField confirmPassword = new HintPasswordField(20);

        public View()
        {
            super();
            this.add(this.password);
            this.add(this.confirmPassword);
        }
    }

    public class HintPasswordField extends JPasswordField implements FocusListener
    {
        public HintPasswordField(int length)
        {
            super(length);
            this.showHint(true);
            this.addFocusListener(this);
        }

        @Override
        public void focusGained(FocusEvent e)
        {
            final String password = new String(getPassword());
            if (password.equals("Password"))
            {
                this.showHint(false);
            }
        }

        @Override
        public void focusLost(FocusEvent e)
        {
            final String password = new String(getPassword());
            if (password.equals(""))
            {
                this.showHint(true);
            }
        }

        private void showHint(boolean showHint)
        {
            if (showHint)   // sets the password field to hide text and show hint
            {
                this.setEchoChar((char) 0);
                this.setForeground(Color.lightGray);
                this.setText("Password");
            }
            else // sets the password field to show password protected text
            {
                this.setEchoChar('*');
                this.setForeground(Color.black);
                this.setText("");
            }
        }
    }
}

Password_Confirmation_Demo Example: (Run Applet)

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

public class Password_Confirmation_Demo extends JApplet
{
    @Override
    public void init()
    {
        this.setContentPane(new View());
    }

    public class View extends JPanel implements ActionListener
    {
        private final JButton submit = new JButton("Submit");
        private final HintPasswordField password = new HintPasswordField(20);
        private final HintPasswordField confirmPassword = new HintPasswordField(20);
        private final JLabel message = new JLabel("");

        public View()
        {
            super();
            final JLabel blank = new JLabel("");
            final JLabel passwordLabel = new JLabel("Password");
            final JLabel confirmPasswordLabel = new JLabel("Confirm Password");
            final JPanel passwordPanel = new JPanel();

            // applet Panel layout
            passwordPanel.setLayout(new GridLayout(3, 2));
            passwordPanel.add(passwordLabel);
            passwordPanel.add(this.password);

            passwordPanel.add(confirmPasswordLabel);
            passwordPanel.add(this.confirmPassword);

            passwordPanel.add(blank);
            passwordPanel.add(this.submit);

            this.setLayout(new BorderLayout());
            this.add("North", passwordPanel);
            this.add("South", this.message);

            this.submit.addActionListener(this);
        }

        @Override
        public void actionPerformed(ActionEvent e)
        {
            final Object source = e.getSource();
            if (source == this.submit)
            {
                final char[] password1 = this.password.getPassword();
                final char[] password2 = this.confirmPassword.getPassword();

                if (Arrays.equals(password1, password2))
                {
                    this.message.setForeground(Color.black);
                    this.message.setText("Match");
                }
                else
                {
                    this.message.setForeground(Color.red);
                    this.message.setText("Different");
                }

                // for security reasons,
                // set both password char arrays
                // to all '0' after use
                Arrays.fill(password1, '0');
                Arrays.fill(password2, '0');
            }
        }
    }

    public class HintPasswordField extends JPasswordField implements FocusListener
    {
        public HintPasswordField(int length)
        {
            super(length);
            this.showHint(true);
            this.addFocusListener(this);
        }

        @Override
        public void focusGained(FocusEvent e)
        {
            final String password = new String(getPassword());
            if (password.equals("Password"))
            {
                this.showHint(false);
            }
        }

        @Override
        public void focusLost(FocusEvent e)
        {
            final String password = new String(getPassword());
            if (password.equals(""))
            {
                this.showHint(true);
            }
        }

        private void showHint(boolean showHint)
        {
            if (showHint)   // sets the password field to hide text and show hint
            {
                this.setEchoChar((char) 0);
                this.setForeground(Color.lightGray);
                this.setText("Password");
            }
            else // sets the password field to show password protected text
            {
                this.setEchoChar('*');
                this.setForeground(Color.black);
                this.setText("");
            }
        }
    }
}

Password_Strength_Demo Example: (Run Applet)

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

public class Password_Strength_Demo extends JApplet
{
    // Define the various strengths that a password can have
    private static enum PasswordStrength
    {
        INVALID,
        WEAK,
        MEDIUM,
        STRONG;
    }

    @Override
    public void init()
    {
        this.setContentPane(new View());
    }

    public class View extends JPanel implements ActionListener
    {
        // Password
        private final HintPasswordField password = new HintPasswordField(15);
        private final HintPasswordField confirmPassword = new HintPasswordField(15);
        private final JButton submit = new JButton("Submit");
        private final JLabel message = new JLabel();

        public View()
        {
            super();

            final JPanel passwordPanel = new JPanel();
            final JPanel confirmPasswordPanel = new JPanel();
            final JPanel passwordsPanel = new JPanel();
            final JPanel submitPanel = new JPanel();
            final JLabel enterPasswordMessage = new JLabel("Enter Password: ");
            final JLabel confirmPasswordMessage = new JLabel("Confirm Password: ");

            // this.passwordPanel layout
            passwordPanel.setLayout(new FlowLayout(FlowLayout.RIGHT));
            passwordPanel.add(enterPasswordMessage);
            passwordPanel.add(this.password);

            // this.confirmPasswordPanel layout
            confirmPasswordPanel.setLayout(new FlowLayout(FlowLayout.RIGHT));
            confirmPasswordPanel.add(confirmPasswordMessage);
            confirmPasswordPanel.add(this.confirmPassword);

            // this.submitPanel layout
            submitPanel.setLayout(new FlowLayout(FlowLayout.RIGHT));
            submitPanel.add(this.submit);

            // this.passwordsPanel layout
            passwordsPanel.setLayout(new GridLayout(3, 1));
            passwordsPanel.add(passwordPanel);
            passwordsPanel.add(confirmPasswordPanel);
            passwordsPanel.add(submitPanel);

            // main Panel layout
            this.setLayout(new BorderLayout());
            this.add("North", passwordsPanel);
            this.add("South", this.message);

            this.submit.addActionListener(this);
        }

        // ActionListener overrides
        @Override
        public void actionPerformed(ActionEvent e)
        {
            final Object source = e.getSource();
            if (source == this.submit)
            {
                this.showText();
            }
        }

        private void showText()
        {
            switch (getPasswordStrength(new String(this.password.getPassword()), new String(this.confirmPassword.getPassword())))
            {
                case INVALID:
                {
                    this.showMessage(Color.red, "Passwords do not match");
                    break;
                }
                case WEAK:
                {
                    this.showMessage(Color.red, "Weak");
                    break;
                }
                case MEDIUM:
                {
                    this.showMessage(Color.blue, "Medium");
                    break;
                }
                case STRONG:
                {
                    this.showMessage(Color.green, "Strong");
                    break;
                }
            }
        }

        private PasswordStrength getPasswordStrength(String password, String confirmedPassword)
        {

            boolean hasAlpha = false;
            boolean hasDecimal = false;
            boolean hasOtherCharacters = false;
            PasswordStrength passwordStrength = PasswordStrength.WEAK;

            if (!password.equals(confirmedPassword))
            {
                passwordStrength = PasswordStrength.INVALID;
                return passwordStrength;
            }

            char c;
            // find out if password contains alpha, decimal or other characters

            for (int i = 0; i < password.length(); i++)
            {
                c = password.charAt(i);
                if ((c >= '0') && (c <= '9'))
                {
                    hasDecimal = true;
                }
                else if (((c >= 'a') && (c <= 'z')) ||
                         ((c >= 'A') && (c <= 'Z')))
                {
                    hasAlpha = true;
                }
                else
                {
                    hasOtherCharacters = true;
                }
            }

            if (hasAlpha && hasDecimal)
            {
                if (hasOtherCharacters)
                {
                    passwordStrength = PasswordStrength.STRONG;
                }
                else
                {
                    passwordStrength = PasswordStrength.MEDIUM;
                }
            }
            else if (hasAlpha || hasDecimal)
            {
                passwordStrength = PasswordStrength.WEAK;
            }

            return passwordStrength;
        }

        private void showMessage(Color color, String message)
        {
            this.message.setForeground(color);
            this.message.setText(message);
        }
    }

    public class HintPasswordField extends JPasswordField implements FocusListener
    {
        public HintPasswordField(int length)
        {
            super(length);
            this.showHint(true);
            this.addFocusListener(this);
        }

        @Override
        public void focusGained(FocusEvent e)
        {
            final String password = new String(getPassword());
            if (password.equals("Password"))
            {
                this.showHint(false);
            }
        }

        @Override
        public void focusLost(FocusEvent e)
        {
            final String password = new String(getPassword());
            if (password.equals(""))
            {
                this.showHint(true);
            }
        }

        private void showHint(boolean showHint)
        {
            if (showHint)   // sets the password field to hide text and show hint
            {
                this.setEchoChar((char) 0);
                this.setForeground(Color.lightGray);
                this.setText("Password");
            }
            else // sets the password field to show password protected text
            {
                this.setEchoChar('*');
                this.setForeground(Color.black);
                this.setText("");
            }
        }
    }
}

TextArea

A text area is a multi-line area used to display text. It can be set to either allow editing or to be read-only.

TextArea example: (Run Applet)

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

public class TextAreaDemo extends JApplet
{
    @Override
    public void init()
    {
        this.setContentPane(new View());
    }

    public class View extends JPanel
    {
        public View()
        {
            final JTextArea area1 = new JTextArea();
            final JTextArea area2 = new JTextArea("We shall set this to be read only.\n");
            final JLabel gap = new JLabel("");

            this.setLayout(new GridLayout(1, 3));

            this.add(area1); 
            this.add(gap);
            this.add(area2);

            area2.setEditable(false);

            area1.append("We can insert text into read/write a text area and \nuse the '\\n' escape code to move to a new line.");
            area2.append("The programmer can insert text into a read only text area, but the user can not.");

            // replace the two letters 'ha' from
            // shall with this new string
            area2.replaceRange("NEW TEXT", 4, 6);
        }
    }
}