https://openjdk.java.net/ 
/*
 * Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package javax.swing;

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

import java.util.Collections;
import java.util.Set;
import java.util.StringTokenizer;

import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.IOException;


A JTextArea is a multi-line area that displays plain text.
It is intended to be a lightweight component that provides source
compatibility with the java.awt.TextArea class where it can
reasonably do so.
You can find information and examples of using all the text components in
Using Text Components,
a section in The Java Tutorial.


This component has capabilities not found in the
java.awt.TextArea class.  The superclass should be
consulted for additional capabilities.
Alternative multi-line text classes with
more capabilities are JTextPane and JEditorPane.


The java.awt.TextArea internally handles scrolling.
JTextArea is different in that it doesn't manage scrolling,
but implements the swing Scrollable interface.  This allows it
to be placed inside a JScrollPane if scrolling
behavior is desired, and used directly if scrolling is not desired.


The java.awt.TextArea has the ability to do line wrapping.
This was controlled by the horizontal scrolling policy.  Since
scrolling is not done by JTextArea directly, backward
compatibility must be provided another way.  JTextArea has
a bound property for line wrapping that controls whether or
not it will wrap lines.  By default, the line wrapping property
is set to false (not wrapped).


java.awt.TextArea has two properties rows
and columns that are used to determine the preferred size.
JTextArea uses these properties to indicate the
preferred size of the viewport when placed inside a JScrollPane
to match the functionality provided by java.awt.TextArea.
JTextArea has a preferred size of what is needed to
display all of the text, so that it functions properly inside of
a JScrollPane.  If the value for rows
or columns is equal to zero,
the preferred size along that axis is used for
the viewport preferred size along the same axis.


The java.awt.TextArea could be monitored for changes by adding
a TextListener for TextEvents.
In the JTextComponent based
components, changes are broadcasted from the model via a
DocumentEvent to DocumentListeners.
The DocumentEvent gives
the location of the change and the kind of change if desired.
The code fragment might look something like:

   DocumentListener myListener = ??;
   JTextArea myArea = ??;
   myArea.getDocument().addDocumentListener(myListener);







Newlines


For a discussion on how newlines are handled, see
DefaultEditorKit.




Warning: Swing is not thread safe. For more
information see Swing's Threading
Policy.


Warning:
Serialized objects of this class will not be compatible with
future Swing releases. The current serialization support is
appropriate for short term storage or RMI between applications running
the same version of Swing.  As of 1.4, support for long term storage
of all JavaBeansTM
has been added to the java.beans package. Please see XMLEncoder. 
Author: Timothy Prinzing
See Also:
@beaninfo
  attribute: isContainer false
description: A multi-line area that displays plain text.
/**
 * A <code>JTextArea</code> is a multi-line area that displays plain text.
 * It is intended to be a lightweight component that provides source
 * compatibility with the <code>java.awt.TextArea</code> class where it can
 * reasonably do so.
 * You can find information and examples of using all the text components in
 * <a href="http://java.sun.com/docs/books/tutorial/uiswing/components/text.html">Using Text Components</a>,
 * a section in <em>The Java Tutorial.</em>
 *
 * <p>
 * This component has capabilities not found in the
 * <code>java.awt.TextArea</code> class.  The superclass should be
 * consulted for additional capabilities.
 * Alternative multi-line text classes with
 * more capabilities are <code>JTextPane</code> and <code>JEditorPane</code>.
 * <p>
 * The <code>java.awt.TextArea</code> internally handles scrolling.
 * <code>JTextArea</code> is different in that it doesn't manage scrolling,
 * but implements the swing <code>Scrollable</code> interface.  This allows it
 * to be placed inside a <code>JScrollPane</code> if scrolling
 * behavior is desired, and used directly if scrolling is not desired.
 * <p>
 * The <code>java.awt.TextArea</code> has the ability to do line wrapping.
 * This was controlled by the horizontal scrolling policy.  Since
 * scrolling is not done by <code>JTextArea</code> directly, backward
 * compatibility must be provided another way.  <code>JTextArea</code> has
 * a bound property for line wrapping that controls whether or
 * not it will wrap lines.  By default, the line wrapping property
 * is set to false (not wrapped).
 * <p>
 * <code>java.awt.TextArea</code> has two properties <code>rows</code>
 * and <code>columns</code> that are used to determine the preferred size.
 * <code>JTextArea</code> uses these properties to indicate the
 * preferred size of the viewport when placed inside a <code>JScrollPane</code>
 * to match the functionality provided by <code>java.awt.TextArea</code>.
 * <code>JTextArea</code> has a preferred size of what is needed to
 * display all of the text, so that it functions properly inside of
 * a <code>JScrollPane</code>.  If the value for <code>rows</code>
 * or <code>columns</code> is equal to zero,
 * the preferred size along that axis is used for
 * the viewport preferred size along the same axis.
 * <p>
 * The <code>java.awt.TextArea</code> could be monitored for changes by adding
 * a <code>TextListener</code> for <code>TextEvent</code>s.
 * In the <code>JTextComponent</code> based
 * components, changes are broadcasted from the model via a
 * <code>DocumentEvent</code> to <code>DocumentListeners</code>.
 * The <code>DocumentEvent</code> gives
 * the location of the change and the kind of change if desired.
 * The code fragment might look something like:
 * <pre>
 *    DocumentListener myListener = ??;
 *    JTextArea myArea = ??;
 *    myArea.getDocument().addDocumentListener(myListener);
 * </pre>
 * <p>
 * <dl>
 * <dt><b><font size=+1>Newlines</font></b>
 * <dd>
 * For a discussion on how newlines are handled, see
 * <a href="text/DefaultEditorKit.html">DefaultEditorKit</a>.
 * </dl>
 *
 * <p>
 * <strong>Warning:</strong> Swing is not thread safe. For more
 * information see <a
 * href="package-summary.html#threading">Swing's Threading
 * Policy</a>.
 * <p>
 * <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with
 * future Swing releases. The current serialization support is
 * appropriate for short term storage or RMI between applications running
 * the same version of Swing.  As of 1.4, support for long term storage
 * of all JavaBeans<sup><font size="-2">TM</font></sup>
 * has been added to the <code>java.beans</code> package.
 * Please see {@link java.beans.XMLEncoder}.
 *
 * @beaninfo
 *   attribute: isContainer false
 * description: A multi-line area that displays plain text.
 *
 * @author  Timothy Prinzing
 * @see JTextPane
 * @see JEditorPane
 */
public class JTextArea extends JTextComponent {

    
See Also:
/**
     * @see #getUIClassID
     * @see #readObject
     */
    private static final String uiClassID = "TextAreaUI";

    
Constructs a new TextArea.  A default model is set, the initial string
is null, and rows/columns are set to 0.

/**
     * Constructs a new TextArea.  A default model is set, the initial string
     * is null, and rows/columns are set to 0.
     */
    public JTextArea() {
        this(null, null, 0, 0);
    }

    
Constructs a new TextArea with the specified text displayed.
A default model is created and rows/columns are set to 0.

Params:
  • text – the text to be displayed, or null
/**
     * Constructs a new TextArea with the specified text displayed.
     * A default model is created and rows/columns are set to 0.
     *
     * @param text the text to be displayed, or null
     */
    public JTextArea(String text) {
        this(null, text, 0, 0);
    }

    
Constructs a new empty TextArea with the specified number of
rows and columns.  A default model is created, and the initial
string is null.

Params:
  • rows – the number of rows >= 0
  • columns – the number of columns >= 0
Throws:
/**
     * Constructs a new empty TextArea with the specified number of
     * rows and columns.  A default model is created, and the initial
     * string is null.
     *
     * @param rows the number of rows >= 0
     * @param columns the number of columns >= 0
     * @exception IllegalArgumentException if the rows or columns
     *  arguments are negative.
     */
    public JTextArea(int rows, int columns) {
        this(null, null, rows, columns);
    }

    
Constructs a new TextArea with the specified text and number
of rows and columns.  A default model is created.

Params:
  • text – the text to be displayed, or null
  • rows – the number of rows >= 0
  • columns – the number of columns >= 0
Throws:
/**
     * Constructs a new TextArea with the specified text and number
     * of rows and columns.  A default model is created.
     *
     * @param text the text to be displayed, or null
     * @param rows the number of rows >= 0
     * @param columns the number of columns >= 0
     * @exception IllegalArgumentException if the rows or columns
     *  arguments are negative.
     */
    public JTextArea(String text, int rows, int columns) {
        this(null, text, rows, columns);
    }

    
Constructs a new JTextArea with the given document model, and defaults
for all of the other arguments (null, 0, 0).

Params:
  • doc –  the model to use
/**
     * Constructs a new JTextArea with the given document model, and defaults
     * for all of the other arguments (null, 0, 0).
     *
     * @param doc  the model to use
     */
    public JTextArea(Document doc) {
        this(doc, null, 0, 0);
    }

    
Constructs a new JTextArea with the specified number of rows
and columns, and the given model.  All of the constructors
feed through this constructor.

Params:
  • doc – the model to use, or create a default one if null
  • text – the text to be displayed, null if none
  • rows – the number of rows >= 0
  • columns – the number of columns >= 0
Throws:
/**
     * Constructs a new JTextArea with the specified number of rows
     * and columns, and the given model.  All of the constructors
     * feed through this constructor.
     *
     * @param doc the model to use, or create a default one if null
     * @param text the text to be displayed, null if none
     * @param rows the number of rows >= 0
     * @param columns the number of columns >= 0
     * @exception IllegalArgumentException if the rows or columns
     *  arguments are negative.
     */
    public JTextArea(Document doc, String text, int rows, int columns) {
        super();
        this.rows = rows;
        this.columns = columns;
        if (doc == null) {
            doc = createDefaultModel();
        }
        setDocument(doc);
        if (text != null) {
            setText(text);
            select(0, 0);
        }
        if (rows < 0) {
            throw new IllegalArgumentException("rows: " + rows);
        }
        if (columns < 0) {
            throw new IllegalArgumentException("columns: " + columns);
        }
        LookAndFeel.installProperty(this,
                                    "focusTraversalKeysForward",
                                    JComponent.
                                    getManagingFocusForwardTraversalKeys());
        LookAndFeel.installProperty(this,
                                    "focusTraversalKeysBackward",
                                    JComponent.
                                    getManagingFocusBackwardTraversalKeys());
    }

    
Returns the class ID for the UI.

See Also:
Returns:the ID ("TextAreaUI")
/**
     * Returns the class ID for the UI.
     *
     * @return the ID ("TextAreaUI")
     * @see JComponent#getUIClassID
     * @see UIDefaults#getUI
     */
    public String getUIClassID() {
        return uiClassID;
    }

    
Creates the default implementation of the model
to be used at construction if one isn't explicitly
given.  A new instance of PlainDocument is returned.

Returns:the default document model
/**
     * Creates the default implementation of the model
     * to be used at construction if one isn't explicitly
     * given.  A new instance of PlainDocument is returned.
     *
     * @return the default document model
     */
    protected Document createDefaultModel() {
        return new PlainDocument();
    }

    
Sets the number of characters to expand tabs to.
This will be multiplied by the maximum advance for
variable width fonts.  A PropertyChange event ("tabSize") is fired
when the tab size changes.

Params:
  • size – number of characters to expand to
See Also:
@beaninfo
  preferred: true
      bound: true
description: the number of characters to expand tabs to
/**
     * Sets the number of characters to expand tabs to.
     * This will be multiplied by the maximum advance for
     * variable width fonts.  A PropertyChange event ("tabSize") is fired
     * when the tab size changes.
     *
     * @param size number of characters to expand to
     * @see #getTabSize
     * @beaninfo
     *   preferred: true
     *       bound: true
     * description: the number of characters to expand tabs to
     */
    public void setTabSize(int size) {
        Document doc = getDocument();
        if (doc != null) {
            int old = getTabSize();
            doc.putProperty(PlainDocument.tabSizeAttribute, new Integer(size));
            firePropertyChange("tabSize", old, size);
        }
    }

    
Gets the number of characters used to expand tabs.  If the document is
null or doesn't have a tab setting, return a default of 8.

Returns:the number of characters
/**
     * Gets the number of characters used to expand tabs.  If the document is
     * null or doesn't have a tab setting, return a default of 8.
     *
     * @return the number of characters
     */
    public int getTabSize() {
        int size = 8;
        Document doc = getDocument();
        if (doc != null) {
            Integer i = (Integer) doc.getProperty(PlainDocument.tabSizeAttribute);
            if (i != null) {
                size = i.intValue();
            }
        }
        return size;
    }

    
Sets the line-wrapping policy of the text area.  If set
to true the lines will be wrapped if they are too long
to fit within the allocated width.  If set to false,
the lines will always be unwrapped.  A PropertyChange
event ("lineWrap") is fired when the policy is changed.
By default this property is false.

Params:
  • wrap – indicates if lines should be wrapped
See Also:
@beaninfo
  preferred: true
      bound: true
description: should lines be wrapped
/**
     * Sets the line-wrapping policy of the text area.  If set
     * to true the lines will be wrapped if they are too long
     * to fit within the allocated width.  If set to false,
     * the lines will always be unwrapped.  A <code>PropertyChange</code>
     * event ("lineWrap") is fired when the policy is changed.
     * By default this property is false.
     *
     * @param wrap indicates if lines should be wrapped
     * @see #getLineWrap
     * @beaninfo
     *   preferred: true
     *       bound: true
     * description: should lines be wrapped
     */
    public void setLineWrap(boolean wrap) {
        boolean old = this.wrap;
        this.wrap = wrap;
        firePropertyChange("lineWrap", old, wrap);
    }

    
Gets the line-wrapping policy of the text area.  If set
to true the lines will be wrapped if they are too long
to fit within the allocated width.  If set to false,
the lines will always be unwrapped.

Returns:if lines will be wrapped
/**
     * Gets the line-wrapping policy of the text area.  If set
     * to true the lines will be wrapped if they are too long
     * to fit within the allocated width.  If set to false,
     * the lines will always be unwrapped.
     *
     * @return if lines will be wrapped
     */
    public boolean getLineWrap() {
        return wrap;
    }

    
Sets the style of wrapping used if the text area is wrapping
lines.  If set to true the lines will be wrapped at word
boundaries (whitespace) if they are too long
to fit within the allocated width.  If set to false,
the lines will be wrapped at character boundaries.
By default this property is false.

Params:
  • word – indicates if word boundaries should be used
  for line wrapping
See Also:
@beaninfo
  preferred: false
      bound: true
description: should wrapping occur at word boundaries
/**
     * Sets the style of wrapping used if the text area is wrapping
     * lines.  If set to true the lines will be wrapped at word
     * boundaries (whitespace) if they are too long
     * to fit within the allocated width.  If set to false,
     * the lines will be wrapped at character boundaries.
     * By default this property is false.
     *
     * @param word indicates if word boundaries should be used
     *   for line wrapping
     * @see #getWrapStyleWord
     * @beaninfo
     *   preferred: false
     *       bound: true
     * description: should wrapping occur at word boundaries
     */
    public void setWrapStyleWord(boolean word) {
        boolean old = this.word;
        this.word = word;
        firePropertyChange("wrapStyleWord", old, word);
    }

    
Gets the style of wrapping used if the text area is wrapping
lines.  If set to true the lines will be wrapped at word
boundaries (ie whitespace) if they are too long
to fit within the allocated width.  If set to false,
the lines will be wrapped at character boundaries.

See Also:
Returns:if the wrap style should be word boundaries
 instead of character boundaries
/**
     * Gets the style of wrapping used if the text area is wrapping
     * lines.  If set to true the lines will be wrapped at word
     * boundaries (ie whitespace) if they are too long
     * to fit within the allocated width.  If set to false,
     * the lines will be wrapped at character boundaries.
     *
     * @return if the wrap style should be word boundaries
     *  instead of character boundaries
     * @see #setWrapStyleWord
     */
    public boolean getWrapStyleWord() {
        return word;
    }

    
Translates an offset into the components text to a
line number.

Params:
  • offset – the offset >= 0
Throws:
  • BadLocationException – thrown if the offset is
  less than zero or greater than the document length.
Returns:the line number >= 0
/**
     * Translates an offset into the components text to a
     * line number.
     *
     * @param offset the offset >= 0
     * @return the line number >= 0
     * @exception BadLocationException thrown if the offset is
     *   less than zero or greater than the document length.
     */
    public int getLineOfOffset(int offset) throws BadLocationException {
        Document doc = getDocument();
        if (offset < 0) {
            throw new BadLocationException("Can't translate offset to line", -1);
        } else if (offset > doc.getLength()) {
            throw new BadLocationException("Can't translate offset to line", doc.getLength()+1);
        } else {
            Element map = getDocument().getDefaultRootElement();
            return map.getElementIndex(offset);
        }
    }

    
Determines the number of lines contained in the area.

Returns:the number of lines > 0
/**
     * Determines the number of lines contained in the area.
     *
     * @return the number of lines > 0
     */
    public int getLineCount() {
        Element map = getDocument().getDefaultRootElement();
        return map.getElementCount();
    }

    
Determines the offset of the start of the given line.

Params:
  • line –  the line number to translate >= 0
Throws:
  • BadLocationException – thrown if the line is
less than zero or greater or equal to the number of
lines contained in the document (as reported by
getLineCount).
Returns:the offset >= 0
/**
     * Determines the offset of the start of the given line.
     *
     * @param line  the line number to translate >= 0
     * @return the offset >= 0
     * @exception BadLocationException thrown if the line is
     * less than zero or greater or equal to the number of
     * lines contained in the document (as reported by
     * getLineCount).
     */
    public int getLineStartOffset(int line) throws BadLocationException {
        int lineCount = getLineCount();
        if (line < 0) {
            throw new BadLocationException("Negative line", -1);
        } else if (line >= lineCount) {
            throw new BadLocationException("No such line", getDocument().getLength()+1);
        } else {
            Element map = getDocument().getDefaultRootElement();
            Element lineElem = map.getElement(line);
            return lineElem.getStartOffset();
        }
    }

    
Determines the offset of the end of the given line.

Params:
  • line –  the line >= 0
Throws:
  • BadLocationException – Thrown if the line is
less than zero or greater or equal to the number of
lines contained in the document (as reported by
getLineCount).
Returns:the offset >= 0
/**
     * Determines the offset of the end of the given line.
     *
     * @param line  the line >= 0
     * @return the offset >= 0
     * @exception BadLocationException Thrown if the line is
     * less than zero or greater or equal to the number of
     * lines contained in the document (as reported by
     * getLineCount).
     */
    public int getLineEndOffset(int line) throws BadLocationException {
        int lineCount = getLineCount();
        if (line < 0) {
            throw new BadLocationException("Negative line", -1);
        } else if (line >= lineCount) {
            throw new BadLocationException("No such line", getDocument().getLength()+1);
        } else {
            Element map = getDocument().getDefaultRootElement();
            Element lineElem = map.getElement(line);
            int endOffset = lineElem.getEndOffset();
            // hide the implicit break at the end of the document
            return ((line == lineCount - 1) ? (endOffset - 1) : endOffset);
        }
    }

    // --- java.awt.TextArea methods ---------------------------------

    
Inserts the specified text at the specified position.  Does nothing
if the model is null or if the text is null or empty.


This method is thread safe, although most Swing methods
are not. Please see
How
to Use Threads for more information.

Params:
  • str – the text to insert
  • pos – the position at which to insert >= 0
Throws:
See Also:
/**
     * Inserts the specified text at the specified position.  Does nothing
     * if the model is null or if the text is null or empty.
     * <p>
     * This method is thread safe, although most Swing methods
     * are not. Please see
     * <A HREF="http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html">How
     * to Use Threads</A> for more information.
     *
     * @param str the text to insert
     * @param pos the position at which to insert >= 0
     * @exception IllegalArgumentException  if pos is an
     *  invalid position in the model
     * @see TextComponent#setText
     * @see #replaceRange
     */
    public void insert(String str, int pos) {
        Document doc = getDocument();
        if (doc != null) {
            try {
                doc.insertString(pos, str, null);
            } catch (BadLocationException e) {
                throw new IllegalArgumentException(e.getMessage());
            }
        }
    }

    
Appends the given text to the end of the document.  Does nothing if
the model is null or the string is null or empty.


This method is thread safe, although most Swing methods
are not. Please see
How
to Use Threads for more information.

Params:
  • str – the text to insert
See Also:
/**
     * Appends the given text to the end of the document.  Does nothing if
     * the model is null or the string is null or empty.
     * <p>
     * This method is thread safe, although most Swing methods
     * are not. Please see
     * <A HREF="http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html">How
     * to Use Threads</A> for more information.
     *
     * @param str the text to insert
     * @see #insert
     */
    public void append(String str) {
        Document doc = getDocument();
        if (doc != null) {
            try {
                doc.insertString(doc.getLength(), str, null);
            } catch (BadLocationException e) {
            }
        }
    }

    
Replaces text from the indicated start to end position with the
new text specified.  Does nothing if the model is null.  Simply
does a delete if the new string is null or empty.


This method is thread safe, although most Swing methods
are not. Please see
How
to Use Threads for more information.

Params:
  • str – the text to use as the replacement
  • start – the start position >= 0
  • end – the end position >= start
Throws:
See Also:
/**
     * Replaces text from the indicated start to end position with the
     * new text specified.  Does nothing if the model is null.  Simply
     * does a delete if the new string is null or empty.
     * <p>
     * This method is thread safe, although most Swing methods
     * are not. Please see
     * <A HREF="http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html">How
     * to Use Threads</A> for more information.
     *
     * @param str the text to use as the replacement
     * @param start the start position >= 0
     * @param end the end position >= start
     * @exception IllegalArgumentException  if part of the range is an
     *  invalid position in the model
     * @see #insert
     * @see #replaceRange
     */
    public void replaceRange(String str, int start, int end) {
        if (end < start) {
            throw new IllegalArgumentException("end before start");
        }
        Document doc = getDocument();
        if (doc != null) {
            try {
                if (doc instanceof AbstractDocument) {
                    ((AbstractDocument)doc).replace(start, end - start, str,
                                                    null);
                }
                else {
                    doc.remove(start, end - start);
                    doc.insertString(start, str, null);
                }
            } catch (BadLocationException e) {
                throw new IllegalArgumentException(e.getMessage());
            }
        }
    }

    
Returns the number of rows in the TextArea.

Returns:the number of rows >= 0
/**
     * Returns the number of rows in the TextArea.
     *
     * @return the number of rows >= 0
     */
    public int getRows() {
        return rows;
    }

    
Sets the number of rows for this TextArea.  Calls invalidate() after
setting the new value.

Params:
  • rows – the number of rows >= 0
Throws:
See Also:
@beaninfo
description: the number of rows preferred for display
/**
     * Sets the number of rows for this TextArea.  Calls invalidate() after
     * setting the new value.
     *
     * @param rows the number of rows >= 0
     * @exception IllegalArgumentException if rows is less than 0
     * @see #getRows
     * @beaninfo
     * description: the number of rows preferred for display
     */
    public void setRows(int rows) {
        int oldVal = this.rows;
        if (rows < 0) {
            throw new IllegalArgumentException("rows less than zero.");
        }
        if (rows != oldVal) {
            this.rows = rows;
            invalidate();
        }
    }

    
Defines the meaning of the height of a row.  This defaults to
the height of the font.

Returns:the height >= 1
/**
     * Defines the meaning of the height of a row.  This defaults to
     * the height of the font.
     *
     * @return the height >= 1
     */
    protected int getRowHeight() {
        if (rowHeight == 0) {
            FontMetrics metrics = getFontMetrics(getFont());
            rowHeight = metrics.getHeight();
        }
        return rowHeight;
    }

    
Returns the number of columns in the TextArea.

Returns:number of columns >= 0
/**
     * Returns the number of columns in the TextArea.
     *
     * @return number of columns >= 0
     */
    public int getColumns() {
        return columns;
    }

    
Sets the number of columns for this TextArea.  Does an invalidate()
after setting the new value.

Params:
  • columns – the number of columns >= 0
Throws:
See Also:
@beaninfo
description: the number of columns preferred for display
/**
     * Sets the number of columns for this TextArea.  Does an invalidate()
     * after setting the new value.
     *
     * @param columns the number of columns >= 0
     * @exception IllegalArgumentException if columns is less than 0
     * @see #getColumns
     * @beaninfo
     * description: the number of columns preferred for display
     */
    public void setColumns(int columns) {
        int oldVal = this.columns;
        if (columns < 0) {
            throw new IllegalArgumentException("columns less than zero.");
        }
        if (columns != oldVal) {
            this.columns = columns;
            invalidate();
        }
    }

    
Gets column width.
The meaning of what a column is can be considered a fairly weak
notion for some fonts.  This method is used to define the width
of a column.  By default this is defined to be the width of the
character m for the font used.  This method can be
redefined to be some alternative amount.

Returns:the column width >= 1
/**
     * Gets column width.
     * The meaning of what a column is can be considered a fairly weak
     * notion for some fonts.  This method is used to define the width
     * of a column.  By default this is defined to be the width of the
     * character <em>m</em> for the font used.  This method can be
     * redefined to be some alternative amount.
     *
     * @return the column width >= 1
     */
    protected int getColumnWidth() {
        if (columnWidth == 0) {
            FontMetrics metrics = getFontMetrics(getFont());
            columnWidth = metrics.charWidth('m');
        }
        return columnWidth;
    }

    // --- Component methods -----------------------------------------

    
Returns the preferred size of the TextArea.  This is the
maximum of the size needed to display the text and the
size requested for the viewport.

Returns:the size
/**
     * Returns the preferred size of the TextArea.  This is the
     * maximum of the size needed to display the text and the
     * size requested for the viewport.
     *
     * @return the size
     */
    public Dimension getPreferredSize() {
        Dimension d = super.getPreferredSize();
        d = (d == null) ? new Dimension(400,400) : d;
        Insets insets = getInsets();

        if (columns != 0) {
            d.width = Math.max(d.width, columns * getColumnWidth() +
                    insets.left + insets.right);
        }
        if (rows != 0) {
            d.height = Math.max(d.height, rows * getRowHeight() +
                                insets.top + insets.bottom);
        }
        return d;
    }

    
Sets the current font.  This removes cached row height and column
width so the new font will be reflected, and calls revalidate().

Params:
  • f – the font to use as the current font
/**
     * Sets the current font.  This removes cached row height and column
     * width so the new font will be reflected, and calls revalidate().
     *
     * @param f the font to use as the current font
     */
    public void setFont(Font f) {
        super.setFont(f);
        rowHeight = 0;
        columnWidth = 0;
    }


    
Returns a string representation of this JTextArea. This method
is intended to be used only for debugging purposes, and the
content and format of the returned string may vary between
implementations. The returned string may be empty but may not
be null.

Returns: a string representation of this JTextArea.
/**
     * Returns a string representation of this JTextArea. This method
     * is intended to be used only for debugging purposes, and the
     * content and format of the returned string may vary between
     * implementations. The returned string may be empty but may not
     * be <code>null</code>.
     *
     * @return  a string representation of this JTextArea.
     */
    protected String paramString() {
        String wrapString = (wrap ?
                             "true" : "false");
        String wordString = (word ?
                             "true" : "false");

        return super.paramString() +
        ",colums=" + columns +
        ",columWidth=" + columnWidth +
        ",rows=" + rows +
        ",rowHeight=" + rowHeight +
        ",word=" + wordString +
        ",wrap=" + wrapString;
    }

    // --- Scrollable methods ----------------------------------------

    
Returns true if a viewport should always force the width of this
Scrollable to match the width of the viewport.  This is implemented
to return true if the line wrapping policy is true, and false
if lines are not being wrapped.

Returns:true if a viewport should force the Scrollables width
to match its own.
/**
     * Returns true if a viewport should always force the width of this
     * Scrollable to match the width of the viewport.  This is implemented
     * to return true if the line wrapping policy is true, and false
     * if lines are not being wrapped.
     *
     * @return true if a viewport should force the Scrollables width
     * to match its own.
     */
    public boolean getScrollableTracksViewportWidth() {
        return (wrap) ? true : super.getScrollableTracksViewportWidth();
    }

    
Returns the preferred size of the viewport if this component
is embedded in a JScrollPane.  This uses the desired column
and row settings if they have been set, otherwise the superclass
behavior is used.

See Also:
Returns:The preferredSize of a JViewport whose view is this Scrollable.
/**
     * Returns the preferred size of the viewport if this component
     * is embedded in a JScrollPane.  This uses the desired column
     * and row settings if they have been set, otherwise the superclass
     * behavior is used.
     *
     * @return The preferredSize of a JViewport whose view is this Scrollable.
     * @see JViewport#getPreferredSize
     */
    public Dimension getPreferredScrollableViewportSize() {
        Dimension size = super.getPreferredScrollableViewportSize();
        size = (size == null) ? new Dimension(400,400) : size;
        Insets insets = getInsets();

        size.width = (columns == 0) ? size.width :
                columns * getColumnWidth() + insets.left + insets.right;
        size.height = (rows == 0) ? size.height :
                rows * getRowHeight() + insets.top + insets.bottom;
        return size;
    }

    
Components that display logical rows or columns should compute
the scroll increment that will completely expose one new row
or column, depending on the value of orientation.  This is implemented
to use the values returned by the getRowHeight and
getColumnWidth methods.


Scrolling containers, like JScrollPane, will use this method
each time the user requests a unit scroll.

Params:
  • visibleRect – the view area visible within the viewport
  • orientation – Either SwingConstants.VERTICAL or
  SwingConstants.HORIZONTAL.
  • direction – Less than zero to scroll up/left,
  greater than zero for down/right.
Throws:
See Also:
Returns:The "unit" increment for scrolling in the specified direction
/**
     * Components that display logical rows or columns should compute
     * the scroll increment that will completely expose one new row
     * or column, depending on the value of orientation.  This is implemented
     * to use the values returned by the <code>getRowHeight</code> and
     * <code>getColumnWidth</code> methods.
     * <p>
     * Scrolling containers, like JScrollPane, will use this method
     * each time the user requests a unit scroll.
     *
     * @param visibleRect the view area visible within the viewport
     * @param orientation Either SwingConstants.VERTICAL or
     *   SwingConstants.HORIZONTAL.
     * @param direction Less than zero to scroll up/left,
     *   greater than zero for down/right.
     * @return The "unit" increment for scrolling in the specified direction
     * @exception IllegalArgumentException for an invalid orientation
     * @see JScrollBar#setUnitIncrement
     * @see #getRowHeight
     * @see #getColumnWidth
     */
    public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction) {
        switch (orientation) {
        case SwingConstants.VERTICAL:
            return getRowHeight();
        case SwingConstants.HORIZONTAL:
            return getColumnWidth();
        default:
            throw new IllegalArgumentException("Invalid orientation: " + orientation);
        }
    }

    
See readObject() and writeObject() in JComponent for more
information about serialization in Swing.

/**
     * See readObject() and writeObject() in JComponent for more
     * information about serialization in Swing.
     */
    private void writeObject(ObjectOutputStream s) throws IOException {
        s.defaultWriteObject();
        if (getUIClassID().equals(uiClassID)) {
            byte count = JComponent.getWriteObjCounter(this);
            JComponent.setWriteObjCounter(this, --count);
            if (count == 0 && ui != null) {
                ui.installUI(this);
            }
        }
    }

/////////////////
// Accessibility support
////////////////


    
Gets the AccessibleContext associated with this JTextArea.
For JTextAreas, the AccessibleContext takes the form of an
AccessibleJTextArea.
A new AccessibleJTextArea instance is created if necessary.

Returns:an AccessibleJTextArea that serves as the
        AccessibleContext of this JTextArea
/**
     * Gets the AccessibleContext associated with this JTextArea.
     * For JTextAreas, the AccessibleContext takes the form of an
     * AccessibleJTextArea.
     * A new AccessibleJTextArea instance is created if necessary.
     *
     * @return an AccessibleJTextArea that serves as the
     *         AccessibleContext of this JTextArea
     */
    public AccessibleContext getAccessibleContext() {
        if (accessibleContext == null) {
            accessibleContext = new AccessibleJTextArea();
        }
        return accessibleContext;
    }

    
This class implements accessibility support for the
JTextArea class.  It provides an implementation of the
Java Accessibility API appropriate to text area user-interface
elements.


Warning:
Serialized objects of this class will not be compatible with
future Swing releases. The current serialization support is
appropriate for short term storage or RMI between applications running
the same version of Swing.  As of 1.4, support for long term storage
of all JavaBeansTM
has been added to the java.beans package. Please see XMLEncoder. 
/**
     * This class implements accessibility support for the
     * <code>JTextArea</code> class.  It provides an implementation of the
     * Java Accessibility API appropriate to text area user-interface
     * elements.
     * <p>
     * <strong>Warning:</strong>
     * Serialized objects of this class will not be compatible with
     * future Swing releases. The current serialization support is
     * appropriate for short term storage or RMI between applications running
     * the same version of Swing.  As of 1.4, support for long term storage
     * of all JavaBeans<sup><font size="-2">TM</font></sup>
     * has been added to the <code>java.beans</code> package.
     * Please see {@link java.beans.XMLEncoder}.
     */
    protected class AccessibleJTextArea extends AccessibleJTextComponent {

        
Gets the state set of this object.

See Also:
Returns:an instance of AccessibleStateSet describing the states
of the object
/**
         * Gets the state set of this object.
         *
         * @return an instance of AccessibleStateSet describing the states
         * of the object
         * @see AccessibleStateSet
         */
        public AccessibleStateSet getAccessibleStateSet() {
            AccessibleStateSet states = super.getAccessibleStateSet();
            states.add(AccessibleState.MULTI_LINE);
            return states;
        }
    }

    // --- variables -------------------------------------------------

    private int rows;
    private int columns;
    private int columnWidth;
    private int rowHeight;
    private boolean wrap;
    private boolean word;

}