Highlighters determine how text is marked to make it stand out. The order in which we discuss the highlighter interfaces may seem counterintuitive. The basic Highlighter interface is so straightforward that you’ll rarely need to work with it directly, so we will describe it later. At this point, we discuss the interface you’re most likely to use first: the Highlighter.HighlightPainter interface.

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

public class LineHighlightPainter implements 
Highlighter.HighlightPainter {

	// Paint a thick line under one line of text, from r 
	// extending rightward to x2.
	private void paintLine(Graphics g, Rectangle r, int x2) {
		int ytop = r.y + r.height - 3;
		g.fillRect(r.x, ytop, x2 - r.x, 3);
	}

	// Paint thick lines under a block of text.
	public void paint(Graphics g, int p0, int p1, Shape bounds, 
JTextComponent c) 
        {
		Rectangle r0 = null, r1 = null, rbounds = bounds.getBounds();
		int xmax = rbounds.x + rbounds.width; 
// x-coordinate of right edge
		try { // Convert positions to pixel coordinates.
			r0 = c.modelToView(p0);
			r1 = c.modelToView(p1);
		} catch (BadLocationException ex) {
			return;
		}
		if ((r0 == null) || (r1 == null))
			return;

		g.setColor(c.getSelectionColor());

		// Special case if p0 and p1 are on the same line
		if (r0.y == r1.y) {
			paintLine(g, r0, r1.x);
			return;
		}

		// First line, from p1 to end-of-line
		paintLine(g, r0, xmax);

		// All the full lines in between, if any 
		// (assumes that all lines have the same height--not 
		// a good assumption with JEditorPane/JTextPane)

		r0.y += r0.height; // Move r0 to next line.
		r0.x = rbounds.x; // Move r0 to left edge.
		while (r0.y < r1.y) {
			paintLine(g, r0, xmax);
			r0.y += r0.height; // Move r0 to next line.
		}

		// Last line, from beginning-of-line to p1
		paintLine(g, r0, r1.x);
	}

	public static void main(String args[]) {

		// Extend DefaultCaret as an anonymous inner class.
		Caret lineHighlightPainterCaret = new DefaultCaret() {
			private Highlighter.HighlightPainter lhp = 
new LineHighlightPainter();

		// Override getSelectionPainter to return 
                // the LineHighlightPainter.
		protected Highlighter.HighlightPainter getSelectionPainter() {
		 return lhp;
			}
		};

		JFrame frame = new JFrame("LineHighlightPainter demo");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		JTextArea area = new JTextArea(9, 45);
		area.setCaret(lineHighlightPainterCaret);
		area.setLineWrap(true);
		area.setWrapStyleWord(true);
		area.setText("This is the story\nof 
the hare who\nlost his spectacles.");
		frame.getContentPane().add(new JScrollPane(area), 
BorderLayout.CENTER);
		frame.pack();
		frame.setVisible(true);
	}
}

JTextPane is a multiline text component that can display text with multiple fonts, colors, and even embedded images. It supports named hierarchical text styles and has other features that can help implement a word processor or a similar application.
 
Technically, JTextPane is a subclass of JEditorPane, but it usually makes more sense to think of JTextPane as a text component in its own right. JEditorPane uses “editor kits” to handle text in various formats (such as HTML or RTF) in a modular way. Use a JEditorPane when you want to view or edit text in one of these formats. Use a JTextPane when you want to handle the text yourself.

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

// Show how icons, components, and text can be added to a JTextPane.
public class PaneInsertionMethods {

	public static void main(String[] args) {

		final JTextPane pane = new JTextPane();

		// Button to insert some text
		JButton textButton = new JButton("Insert Text");
		textButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent event) {
				pane.replaceSelection("text");
			}
		});

		// Button to insert an icon
		final ImageIcon icon = new ImageIcon("bluepaw.gif");
		JButton iconButton = new JButton(icon);
		iconButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent event) {
				pane.insertIcon(icon);
			}
		});

		// Button to insert a button
		JButton buttonButton = new JButton("Insert Button");
		buttonButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent event) {
				pane.insertComponent(new JButton("Click Me"));
			}
		});

		// Layout
		JPanel buttons = new JPanel();
		buttons.add(textButton);
		buttons.add(iconButton);
		buttons.add(buttonButton);

		JFrame frame = new JFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.getContentPane().add(pane, BorderLayout.CENTER);
		frame.getContentPane().add(buttons, BorderLayout.SOUTH);
		frame.setSize(360, 180);
		frame.setVisible(true);
	}
}

Swing provides extended functionality for text fields through the JFormattedTextField class introduced in SDK 1.4. A JFormattedTextField can display its value in a friendly (and locale-specific) way, enforce restrictions on its value, be used to edit non-String objects, and permit its value (or part of its value) to be incremented or decremented with the keyboard.

import javax.swing.*;

public class SimpleFTF extends JPanel {

	public SimpleFTF() {
		JFormattedTextField ftf[] = new JFormattedTextField[7];
                // Description of each field
		String des[] = new String[ftf.length]; 

		des[0] = "Date";
		ftf[0] = new JFormattedTextField(new java.util.Date());

		des[1] = "Integer";
		ftf[1] = new JFormattedTextField(new Integer(90032221));

		des[2] = "Float";
		ftf[2] = new JFormattedTextField(new Float(3.14));
                // Manually specify a NumberFormat.
		des[3] = "Float work-around"; 
		ftf[3] = 
new JFormattedTextField(java.text.NumberFormat.getInstance());
		ftf[3].setValue(new Float(3.14));

		des[4] = "currency";
		ftf[4] = new JFormattedTextField(java.text.NumberFormat.
                         getCurrencyInstance());
		ftf[4].setValue(new Float(5.99));

		des[5] = "percent";
		ftf[5] = new JFormattedTextField(java.text.NumberFormat.
                         getPercentInstance());
		ftf[5].setValue(new Float(0.33));

                // Works via 1-arg String constructor and // toString( )
		des[6] = "java.net.URL"; 
					
		java.net.URL u = null;
		try {
			u = new java.net.URL("http://www.ora.com/");
		} catch (java.net.MalformedURLException ignored) {
		}
		ftf[6] = new JFormattedTextField(u);
		ftf[6].setColumns(24);

		// Add each ftf[] to a BoxLayout.
		setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
		for (int j = 0; j < ftf.length; j += 1) {
			JPanel borderPanel = 
new JPanel(new java.awt.BorderLayout());
			borderPanel.setBorder(
new javax.swing.border.TitledBorder(des[j]));
			borderPanel.add(ftf[j], java.awt.BorderLayout.CENTER);
			add(borderPanel);
		}
	}

	public static void main(String argv[]) {
		String localeString = 
java.util.Locale.getDefault().getDisplayName();
		JFrame f = new JFrame("SimpleFTF " + localeString);
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		f.setContentPane(new SimpleFTF());
		f.pack();
		f.setVisible(true);
	}
}

The JTextArea class displays multiple lines of text in a single font and style. Its default behavior is not to wrap lines of text, but line-wrapping can be enabled on word or character boundaries.
 
Like all Swing JTextComponents (but unlike java.awt.TextArea), JTextArea lacks integrated scrollbars. Fortunately, it is easy to embed a JTextArea inside a JScrollPane for seamless scrolling. (JTextArea implements the Scrollable interface, so JScrollPane can be intelligent about scrolling it.)
 
JTextArea handles newlines in a cross-platform way. Line separators in text files can be newline (\n), carriage return (\r), or carriage return newline (\r\n), depending on the platform. Swing’s text components remember which line separator was originally used, but always use a newline character to represent one in memory. So always use \n when working with the content of a text component. When writing the content back to disk (or to whatever destination you give the write( ) method), the text component translates newlines back to the remembered type. If there is no remembered type (because the content was created from scratch), newlines are translated to the value of the line.separator system property.

import javax.swing.*;
import javax.swing.text.*;

public class OffsetTest {
	public static void main(String[] args) {
		JTextArea ta = new JTextArea();
		ta.setLineWrap(true);
		ta.setWrapStyleWord(true);
		JScrollPane scroll = new JScrollPane(ta);

		// Add three lines of text to the JTextArea.
		ta.append("The first line.\n");
		ta.append("Line Two!\n");
		ta.append("This is the 3rd line of this document.");

		// Print some results.
		try {
			for (int n = 0; n < ta.getLineCount(); n += 1)
				System.out.println("line " + n + " starts at " + 
                               ta.getLineStartOffset(n) + ", ends at "
						+ ta.getLineEndOffset(n));
			System.out.println();

			int n = 0;
			while (true) {
				System.out.print("offset " + n + " is on ");
				System.out.println("line " + ta.getLineOfOffset(n));
				n += 13;
			}
		} catch (BadLocationException ex) {
			System.out.println(ex);
		}

		// Layout
		JFrame f = new JFrame();
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		f.getContentPane().add(scroll, java.awt.BorderLayout.CENTER);
		f.setSize(150, 150);
		f.setVisible(true);
	}
}

One of the most common user-interface constructs is the basic form. Typically, forms are made up of labels and fields, with the label describing the text to be entered in the field. Here’s a primitive TextForm class that shows the use of mnemonics, tooltips, and basic accessibility support. Note that we call setLabelFor( ) to associate each label with a text field. This association allows the mnemonics to set the focus and, together with setToolTipText( ), supports accessibility.

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

// A simple label/field form panel
public class TextForm extends JPanel {

	private JTextField[] fields;

	// Create a form with the specified labels, tooltips, and sizes.
	public TextForm(String[] labels, char[] mnemonics, int[] widths, 
                        String[] tips) {
		super(new BorderLayout());
		JPanel labelPanel = new JPanel(new GridLayout(labels.length, 1));
		JPanel fieldPanel = new JPanel(new GridLayout(labels.length, 1));
		add(labelPanel, BorderLayout.WEST);
		add(fieldPanel, BorderLayout.CENTER);
		fields = new JTextField[labels.length];

		for (int i = 0; i < labels.length; i += 1) {
			fields[i] = new JTextField();
			if (i < tips.length)
				fields[i].setToolTipText(tips[i]);
			if (i < widths.length)
				fields[i].setColumns(widths[i]);

			JLabel lab = new JLabel(labels[i], JLabel.RIGHT);
			lab.setLabelFor(fields[i]);
			if (i < mnemonics.length)
				lab.setDisplayedMnemonic(mnemonics[i]);

			labelPanel.add(lab);
			JPanel p = new JPanel(new FlowLayout(FlowLayout.LEFT));
			p.add(fields[i]);
			fieldPanel.add(p);
		}
	}

	public String getText(int i) {
		return (fields[i].getText());
	}

	public static void main(String[] args) {
		String[] labels = { "First Name", "Middle Initial", "Last Name", 
                                    "Age" };
		char[] mnemonics = { 'F', 'M', 'L', 'A' };
		int[] widths = { 15, 1, 15, 3 };
		String[] descs = { "First Name", "Middle Initial", "Last Name", 
                                    "Age" };

		final TextForm form = new TextForm(labels, mnemonics, widths, 
descs);

		JButton submit = new JButton("Submit Form");

		submit.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				System.out.println(form.getText(0) + " " + 
                          form.getText(1) + ". " + form.getText(2) + 
                          ", age " + form.getText(3));
			}
		});

		JFrame f = new JFrame("Text Form Example");
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		f.getContentPane().add(form, BorderLayout.NORTH);
		JPanel p = new JPanel();
		p.add(submit);
		f.getContentPane().add(p, BorderLayout.SOUTH);
		f.pack();
		f.setVisible(true);
	}
}

JTextField allows the user to enter a single line of text, scrolling the text if its size exceeds the physical size of the field. A JTextField fires an ActionEvent to any registered ActionListeners (including the Action set via the setAction( ) method, if any) when the user presses the Enter key.
 
JTextFields (and all JTextComponents) are automatically installed with a number of behaviors appropriate to the L&F, so cut/copy/paste, special cursor movement keys, and text-selection gestures should work without any extra intervention on your part.

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

public class JTextFieldExample {

	public static void main(String[] args) {

		final JTextField tf = new JTextField("press <enter>", 20);
		tf.setHorizontalAlignment(JTextField.RIGHT);

		tf.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				int old = tf.getHorizontalAlignment();
				if (old == JTextField.LEFT)
					tf.setHorizontalAlignment(JTextField.RIGHT);
				if (old == JTextField.RIGHT)
					tf.setHorizontalAlignment(JTextField.CENTER);
				if (old == JTextField.CENTER)
					tf.setHorizontalAlignment(JTextField.LEFT);
			}
		});

		JFrame frame = new JFrame("JTextFieldExample");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.getContentPane().setLayout(new java.awt.FlowLayout());
		frame.getContentPane().add(tf);
		frame.setSize(275, 75);
		frame.setVisible(true);
		tf.requestFocus();
	}
}

Swing provides an extensive collection of classes for working with text in user interfaces. In fact, because there’s so much provided for working with text, Swing’s creators placed most of it into its own package: javax.swing.text. This package’s dozens of interfaces and classes (plus the six concrete component classes in javax.swing) provide a rich set of text-based models and components complex enough to allow endless customization yet simple to use in the common case.

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

public class TextComponentSampler extends JFrame {

	public static String word = "portmeiron";
	public static String markup = "Questions are <font size='+1' 
color='blue'>a burden</font> to others,\n"+ "answers <font size='+2' 
color='red'>a prison</font> for oneself.";

	public TextComponentSampler() {
		super("TextComponentSampler");

		JTextField tf = new JTextField(word, 12);
		JPasswordField pf = new JPasswordField(word, 12);

		MaskFormatter formatter = null;
		try {
			formatter = new MaskFormatter("UUUUU");
		} catch (java.text.ParseException ex) {
		}
		JFormattedTextField ftf = new JFormattedTextField(formatter);
		ftf.setColumns(12);
		ftf.setValue(word);

		JTextArea ta1 = new JTextArea(markup);
		JScrollPane scroll1 = new JScrollPane(ta1);

		JTextArea ta2 = new JTextArea(markup);
		ta2.setLineWrap(true);
		ta2.setWrapStyleWord(true);
		JScrollPane scroll2 = new JScrollPane(ta2);

		JTextPane tp = new JTextPane();
		tp.setText(markup);
		// Create an AttributeSet with which to change color and font.
		SimpleAttributeSet attrs = new SimpleAttributeSet();
		StyleConstants.setForeground(attrs, Color.blue);
		StyleConstants.setFontFamily(attrs, "Serif");
		// Apply the AttributeSet to a few blocks of text.
		StyledDocument sdoc = tp.getStyledDocument();
		sdoc.setCharacterAttributes(14, 29, attrs, false);
		sdoc.setCharacterAttributes(51, 7, attrs, false);
		sdoc.setCharacterAttributes(78, 28, attrs, false);
		sdoc.setCharacterAttributes(114, 7, attrs, false);
		JScrollPane scroll3 = new JScrollPane(tp);

		JEditorPane ep1 = new JEditorPane("text/plain", markup);
		JScrollPane scroll4 = new JScrollPane(ep1);

		JEditorPane ep2 = new JEditorPane("text/html", markup);
		JScrollPane scroll5 = new JScrollPane(ep2);

		// Done creating text components; now lay them out and 
                // make them pretty.
		JPanel panel_tf = new JPanel();
		JPanel panel_pf = new JPanel();
		JPanel panel_ftf = new JPanel();
		panel_tf.add(tf);
		panel_pf.add(pf);
		panel_ftf.add(ftf);

		panel_tf.setBorder(new TitledBorder("JTextField"));
		panel_pf.setBorder(new TitledBorder("JPasswordField"));
		panel_ftf.setBorder(new TitledBorder("JFormattedTextField"));
		scroll1.setBorder(new TitledBorder("JTextArea (line wrap off)"));
		scroll2.setBorder(new TitledBorder("JTextArea (line wrap on)"));
		scroll3.setBorder(new TitledBorder("JTextPane"));
		scroll4.setBorder(new TitledBorder("JEditorPane (text/plain)"));
		scroll5.setBorder(new TitledBorder("JEditorPane (text/html)"));

		JPanel pan = new JPanel(new FlowLayout(FlowLayout.LEFT));
		pan.add(panel_tf);
		pan.add(panel_pf);
		pan.add(panel_ftf);

		Container contentPane = getContentPane();
		contentPane.setLayout(new GridLayout(2, 3, 8, 8));

		contentPane.add(pan);
		contentPane.add(scroll1);
		contentPane.add(scroll2);
		contentPane.add(scroll3);
		contentPane.add(scroll4);
		contentPane.add(scroll5);
	}

	public static void main(String args[]) {
		JFrame frame = new TextComponentSampler();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setSize(600, 450);
		frame.setVisible(true);
	}
}