public PlainDocument() 
{
        this(new GapContent());
}

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

 public PlainDocument(Content c) 
{
        super(c);
        putProperty(tabSizeAttribute, Integer.valueOf(8));
        defaultRoot = createDefaultRoot();
}

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

 protected AbstractElement createDefaultRoot() 
{
        BranchElement map = (BranchElement) createBranchElement(null, null);
        Element line = createLeafElement(map, null, 0, 1);
        Element[] lines = new Element[1];
        lines[0] = line;
        map.replace(0, 0, lines);
        return map;
}

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

 public Element getDefaultRootElement() 
{
        return defaultRoot;
}

Gets the default root element for the document model.

 public Element getParagraphElement(int pos) 
{
        Element lineMap = getDefaultRootElement();
        return lineMap.getElement( lineMap.getElementIndex( pos ) );
}

Get the paragraph element containing the given position. Since this document only models lines, it returns the line instead.

 public  void insertString(int offs,
    String str,
    AttributeSet a) throws BadLocationException 
{
        // fields don't want to have multiple lines.  We may provide a field-specific
        // model in the future in which case the filtering logic here will no longer
        // be needed.
        Object filterNewlines = getProperty("filterNewlines");
        if ((filterNewlines instanceof Boolean) && filterNewlines.equals(Boolean.TRUE)) {
            if ((str != null) && (str.indexOf('\n')  >= 0)) {
                StringBuilder filtered = new StringBuilder(str);
                int n = filtered.length();
                for (int i = 0; i <  n; i++) {
                    if (filtered.charAt(i) == '\n') {
                        filtered.setCharAt(i, ' ');
                    }
                }
                str = filtered.toString();
            }
        }
        super.insertString(offs, str, a);
}

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 How to Use Threads for more information.

 protected  void insertUpdate(DefaultDocumentEvent chng,
    AttributeSet attr) 
{
        removed.removeAllElements();
        added.removeAllElements();
        BranchElement lineMap = (BranchElement) getDefaultRootElement();
        int offset = chng.getOffset();
        int length = chng.getLength();
        if (offset  > 0) {
          offset -= 1;
          length += 1;
        }
        int index = lineMap.getElementIndex(offset);
        Element rmCandidate = lineMap.getElement(index);
        int rmOffs0 = rmCandidate.getStartOffset();
        int rmOffs1 = rmCandidate.getEndOffset();
        int lastOffset = rmOffs0;
        try {
            if (s == null) {
                s = new Segment();
            }
            getContent().getChars(offset, length, s);
            boolean hasBreaks = false;
            for (int i = 0; i <  length; i++) {
                char c = s.array[s.offset + i];
                if (c == '\n') {
                    int breakOffset = offset + i + 1;
                    added.addElement(createLeafElement(lineMap, null, lastOffset, breakOffset));
                    lastOffset = breakOffset;
                    hasBreaks = true;
                }
            }
            if (hasBreaks) {
                removed.addElement(rmCandidate);
                if ((offset + length == rmOffs1) && (lastOffset != rmOffs1) &&
                    ((index+1) <  lineMap.getElementCount())) {
                    Element e = lineMap.getElement(index+1);
                    removed.addElement(e);
                    rmOffs1 = e.getEndOffset();
                }
                if (lastOffset <  rmOffs1) {
                    added.addElement(createLeafElement(lineMap, null, lastOffset, rmOffs1));
                }
                Element[] aelems = new Element[added.size()];
                added.copyInto(aelems);
                Element[] relems = new Element[removed.size()];
                removed.copyInto(relems);
                ElementEdit ee = new ElementEdit(lineMap, index, relems, aelems);
                chng.addEdit(ee);
                lineMap.replace(index, relems.length, aelems);
            }
            if (Utilities.isComposedTextAttributeDefined(attr)) {
                insertComposedTextUpdate(chng, attr);
            }
        } catch (BadLocationException e) {
            throw new Error("Internal error: " + e.toString());
        }
        super.insertUpdate(chng, 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.

 protected  void removeUpdate(DefaultDocumentEvent chng) 
{
        removed.removeAllElements();
        BranchElement map = (BranchElement) getDefaultRootElement();
        int offset = chng.getOffset();
        int length = chng.getLength();
        int line0 = map.getElementIndex(offset);
        int line1 = map.getElementIndex(offset + length);
        if (line0 != line1) {
            // a line was removed
            for (int i = line0; i < = line1; i++) {
                removed.addElement(map.getElement(i));
            }
            int p0 = map.getElement(line0).getStartOffset();
            int p1 = map.getElement(line1).getEndOffset();
            Element[] aelems = new Element[1];
            aelems[0] = createLeafElement(map, null, p0, p1);
            Element[] relems = new Element[removed.size()];
            removed.copyInto(relems);
            ElementEdit ee = new ElementEdit(map, line0, relems, aelems);
            chng.addEdit(ee);
            map.replace(line0, relems.length, aelems);
        } else {
            //Check for the composed text element
            Element line = map.getElement(line0);
            if (!line.isLeaf()) {
                Element leaf = line.getElement(line.getElementIndex(offset));
                if (Utilities.isComposedTextElement(leaf)) {
                    Element[] aelem = new Element[1];
                    aelem[0] = createLeafElement(map, null,
                        line.getStartOffset(), line.getEndOffset());
                    Element[] relem = new Element[1];
                    relem[0] = line;
                    ElementEdit ee = new ElementEdit(map, line0, relem, aelem);
                    chng.addEdit(ee);
                    map.replace(line0, 1, aelem);
                }
            }
        }
        super.removeUpdate(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.