PlainDocument (Java Platform SE 8 )
Keywords: javax.swing.text.PlainDocument class
Date: 2026-04-22

javax.swing.text

## Class PlainDocument

- java.lang.Object
- - javax.swing.text.AbstractDocument
  - - javax.swing.text.PlainDocument

- All Implemented Interfaces:
    Serializable, Document

      public class PlainDocument
      extends AbstractDocument

  A plain document that maintains no character attributes. The default element structure for this document is a map of the lines in the text. The Element returned by getDefaultRootElement is a map of the lines, and each child element represents a line. This model does not maintain any character level attributes, but each line can be tagged with an arbitrary set of attributes. Line to offset, and offset to line translations can be quickly performed using the default root element. The structure information of the DocumentEvent's fired by edits will indicate the line structure changes.

  The default content storage management is performed by a gapped buffer implementation (GapContent). It supports editing reasonably large documents with good efficiency when the edits are contiguous or clustered, as is typical.

  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 JavaBeans™ has been added to the `java.beans` package. Please see `XMLEncoder`.

  See Also:
    `Document`, `AbstractDocument`

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from class javax.swing.text.AbstractDocument

      `AbstractDocument.AbstractElement, AbstractDocument.AttributeContext, AbstractDocument.BranchElement, AbstractDocument.Content, AbstractDocument.DefaultDocumentEvent, AbstractDocument.ElementEdit, AbstractDocument.LeafElement`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static String` | `lineLimitAttribute` Name of the attribute that specifies the maximum length of a line, if there is a maximum length.
    `static String` | `tabSizeAttribute` Name of the attribute that specifies the tab size for tabs contained in the content.

    - ### Fields inherited from class javax.swing.text.AbstractDocument

      `BAD_LOCATION, BidiElementName, ContentElementName, ElementNameAttribute, listenerList, ParagraphElementName, SectionElementName`

    - ### Fields inherited from interface javax.swing.text.Document

      `StreamDescriptionProperty, TitleProperty`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `PlainDocument()` Constructs a plain text document.
    `PlainDocument(AbstractDocument.Content c)` Constructs a plain text document.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected AbstractDocument.AbstractElement` | `createDefaultRoot()` Creates the root element to be used to represent the default document structure.
    `Element` | `getDefaultRootElement()` Gets the default root element for the document model.
    `Element` | `getParagraphElement(int pos)` Get the paragraph element containing the given position.
    `void` | `insertString(int offs, String str, AttributeSet a)` Inserts some content into the document.
    `protected void` | `insertUpdate(AbstractDocument.DefaultDocumentEvent chng, AttributeSet attr)` Updates document structure as a result of text insertion.
    `protected void` | `removeUpdate(AbstractDocument.DefaultDocumentEvent chng)` Updates any document structure as a result of text removal.

    - ### Methods inherited from class javax.swing.text.AbstractDocument

      `addDocumentListener, addUndoableEditListener, createBranchElement, createLeafElement, createPosition, dump, fireChangedUpdate, fireInsertUpdate, fireRemoveUpdate, fireUndoableEditUpdate, getAsynchronousLoadPriority, getAttributeContext, getBidiRootElement, getContent, getCurrentWriter, getDocumentFilter, getDocumentListeners, getDocumentProperties, getEndPosition, getLength, getListeners, getProperty, getRootElements, getStartPosition, getText, getText, getUndoableEditListeners, postRemoveUpdate, putProperty, readLock, readUnlock, remove, removeDocumentListener, removeUndoableEditListener, render, replace, setAsynchronousLoadPriority, setDocumentFilter, setDocumentProperties, writeLock, writeUnlock`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### tabSizeAttribute

          public static final String tabSizeAttribute

      Name of the attribute that specifies the tab size for tabs contained in the content. The type for the value is Integer.
      See Also:
        Constant Field Values

    - #### lineLimitAttribute

          public static final String lineLimitAttribute

      Name of the attribute that specifies the maximum length of a line, if there is a maximum length. The type for the value is Integer.
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### PlainDocument

          public PlainDocument()

      Constructs a plain text document. A default model using `GapContent` is constructed and set.

    - #### PlainDocument

          public PlainDocument(AbstractDocument.Content c)

      Constructs a plain text document. A default root element is created, and the tab size set to 8.
      Parameters:
        `c` - the container for the content

  - ### Method Detail

    - #### insertString

          public void insertString(int offs,
                                   String str,
                                   AttributeSet a)
                            throws BadLocationException

      Inserts some content into the document. Inserting content causes a write lock to be held while the actual changes are taking place, followed by notification to the observers on the thread that grabbed the write lock.

      This method is thread safe, although most Swing methods are not. Please see Concurrency in Swing for more information.

      Specified by:
        `insertString` in interface `Document`
      Overrides:
        `insertString` in class `AbstractDocument`
      Parameters:
        `offs` - the starting offset >= 0
        `str` - the string to insert; does nothing with null/empty strings
        `a` - the attributes for the inserted content
      Throws:
        `BadLocationException` - the given insert position is not a valid position within the document
      See Also:
        `Document.insertString(int, java.lang.String, javax.swing.text.AttributeSet)`

    - #### getDefaultRootElement

          public Element getDefaultRootElement()

      Gets the default root element for the document model.
      Specified by:
        `getDefaultRootElement` in interface `Document`
      Specified by:
        `getDefaultRootElement` in class `AbstractDocument`
      Returns:
        the root
      See Also:
        `Document.getDefaultRootElement()`

    - #### createDefaultRoot

          protected AbstractDocument.AbstractElement createDefaultRoot()

      Creates the root element to be used to represent the default document structure.
      Returns:
        the element base

    - #### getParagraphElement

          public Element getParagraphElement(int pos)

      Get the paragraph element containing the given position. Since this document only models lines, it returns the line instead.
      Specified by:
        `getParagraphElement` in class `AbstractDocument`
      Parameters:
        `pos` - the starting offset >= 0
      Returns:
        the element

    - #### insertUpdate

          protected void insertUpdate(AbstractDocument.DefaultDocumentEvent chng,
                                      AttributeSet attr)

      Updates document structure as a result of text insertion. This will happen within a write lock. Since this document simply maps out lines, we refresh the line map.
      Overrides:
        `insertUpdate` in class `AbstractDocument`
      Parameters:
        `chng` - the change event describing the dit
        `attr` - the set of attributes for the inserted text

    - #### removeUpdate

          protected void removeUpdate(AbstractDocument.DefaultDocumentEvent chng)

      Updates any document structure as a result of text removal. This will happen within a write lock. Since the structure represents a line map, this just checks to see if the removal spans lines. If it does, the two lines outside of the removal area are joined together.
      Overrides:
        `removeUpdate` in class `AbstractDocument`
      Parameters:
        `chng` - the change event describing the edit

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