public JTextPane() 
{
        setEditorKit(new StyledEditorKit());
}

 public JTextPane(StyledDocument doc) 
{
        this();
        if (doc == null) {
            throw new NullPointerException();
        }
}

 public Style addStyle(String styleName,
    Style parent) 
{
        return getStyledDocument().addStyle(styleName, parent);
}

 protected EditorKit createDefaultEditorKit() 
{
        return new StyledEditorKit();
}

 public AttributeSet getCharacterAttributes() 
{
        final int position = getCaretPosition();
        if (position <  0) {
            return null;
        }
        return this.getStyledDocument().getCharacterElement(position)
                .getAttributes();
}

 public MutableAttributeSet getInputAttributes() 
{
        return getStyledEditorKit().getInputAttributes();
}

 public Style getLogicalStyle() 
{
        final int position = getCaretPosition();
        if (position <  0) {
            return null;
        }
        return getStyledDocument().getLogicalStyle(position);
}

 public AttributeSet getParagraphAttributes() 
{
        final int position = getCaretPosition();
        if (position <  0) {
            return null;
        }
        return getStyledDocument().getParagraphElement(position)
                .getAttributes();
}

 public Style getStyle(String styleName) 
{
        return getStyledDocument().getStyle(styleName);
}

 public StyledDocument getStyledDocument() 
{
        return (StyledDocument)getDocument();
}

 protected final StyledEditorKit getStyledEditorKit() 
{
        return (StyledEditorKit) getEditorKit();
}

 public String getUIClassID() 
{
        return uiClassID;
}

 public synchronized  void insertComponent(Component c) 
{
        final MutableAttributeSet attrs = new SimpleAttributeSet();
        StyleConstants.setComponent(attrs, c);
        replaceObject(getStyledDocument(),
                     getSelectionStart(),
                     getSelectionEnd(),
                     attrs);
}

To insert component we should insert in the document whitespace with special attribute StyleConstants.ComponentAttribute

 public synchronized  void insertIcon(Icon g) 
{
        final MutableAttributeSet attrs = new SimpleAttributeSet();
        StyleConstants.setIcon(attrs, g);
        replaceObject(getStyledDocument(),
                getSelectionStart(),
                getSelectionEnd(),
                attrs);
}

To insert icon we should insert in the document whitespace with special attribute StyleConstants.IconAttribute

 public  void removeStyle(String styleName) 
{
        getStyledDocument().removeStyle(styleName);
}

 public  void replaceSelection(String content) 
{
        if (!isEditable()) {
            new DefaultEditorKit.BeepAction().actionPerformed(null);
            return;
        }
        final int start = getSelectionStart();
        final int end = getSelectionEnd();
        final StyledDocument doc = getStyledDocument();
        AttributeSet attrs;
        try {
            if (start != end) {
                attrs = doc.getCharacterElement(start).getAttributes();
                doc.remove(start, end - start);
                if (StyleConstants.getIcon(attrs) != null) {
                    final MutableAttributeSet newAttrs =
                        new SimpleAttributeSet(attrs);
                    newAttrs.removeAttribute(StyleConstants.IconAttribute);
                    newAttrs.removeAttribute(AbstractDocument
                                             .ElementNameAttribute);
                    attrs = newAttrs;
                }
                if (StyleConstants.getComponent(attrs) != null) {
                    final MutableAttributeSet newAttrs =
                        new SimpleAttributeSet(attrs);
                    newAttrs.removeAttribute(StyleConstants.ComponentAttribute);
                    newAttrs.removeAttribute(AbstractDocument
                                             .ElementNameAttribute);
                    attrs = newAttrs;
                }
            } else {
                attrs = getInputAttributes();
            }
            if (content != null) {
                doc.insertString(start, content, attrs);
            }
        } catch (BadLocationException e) {
        }
}

This method differs from JEditorPane.replaceSelection only in one case. If there is selection the replacement text should have not the attributes currently defined for input, but the attributes of the first selected symbol.

 public synchronized  void setCharacterAttributes(AttributeSet attr,
    boolean replace) 
{
         TextUtils.setCharacterAttributes(attr, replace, this,
                                          getStyledDocument(),
                                          getInputAttributes());
}

 public  void setDocument(Document doc) 
{
        if (doc instanceof StyledDocument) {
            super.setDocument(doc);
        } else {
            throw new IllegalArgumentException(Messages.getString("swing.48", "StyledDocument")); //$NON-NLS-1$ //$NON-NLS-2$
        }
}

 public final  void setEditorKit(EditorKit kit) 
{
        if (kit instanceof StyledEditorKit) {
            super.setEditorKit(kit);
        } else {
            throw new IllegalArgumentException(Messages.getString("swing.49","StyledEditorKit")); //$NON-NLS-1$ //$NON-NLS-2$
        }
}

 public  void setLogicalStyle(Style s) 
{
        getStyledDocument().setLogicalStyle(getCaretPosition(), s);
}

 public synchronized  void setParagraphAttributes(AttributeSet attr,
    boolean replace) 
{
        TextUtils.setParagraphAttributes(attr, replace, this,
                                         getStyledDocument());
}

 public  void setStyledDocument(StyledDocument doc) 
{
        super.setDocument(doc);
}