Java Utililty Methods JTextComponent

List of utility methods to do JTextComponent

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Description

The list of methods to do JTextComponent are organized into topic(s).

Method

voidaddChangeListener(JTextComponent text, ChangeListener changeListener)
Installs a listener to receive notification when the text of any JTextComponent is changed. 
Objects.requireNonNull(text);
Objects.requireNonNull(changeListener);
DocumentListener dl = new DocumentListener() {
    private int lastChange = 0, lastNotifiedChange = 0;
    @Override
    public void insertUpdate(DocumentEvent e) {
        changedUpdate(e);
    @Override
    public void removeUpdate(DocumentEvent e) {
        changedUpdate(e);
    @Override
    public void changedUpdate(DocumentEvent e) {
        lastChange++;
        SwingUtilities.invokeLater(() -> {
            if (lastNotifiedChange != lastChange) {
                lastNotifiedChange = lastChange;
                changeListener.stateChanged(new ChangeEvent(text));
        });
};
text.addPropertyChangeListener("document", (PropertyChangeEvent e) -> {
    Document d1 = (Document) e.getOldValue();
    Document d2 = (Document) e.getNewValue();
    if (d1 != null)
        d1.removeDocumentListener(dl);
    if (d2 != null)
        d2.addDocumentListener(dl);
    dl.changedUpdate(null);
});
Document d = text.getDocument();
if (d != null)
    d.addDocumentListener(dl);
voidaddJTextComponentListeners(JTextComponent c, Object... objs)
add J Text Component Listeners 
if (c == null)
    return;
addJContainerListeners(c, objs);
CaretListener caretListener = search(objs, CaretListener.class);
InputMethodListener inputMethodListener = search(objs, InputMethodListener.class);
if (caretListener != null)
    c.addCaretListener(caretListener);
if (inputMethodListener != null)
...
voidaddTextListener(JTextComponent c, Runnable listener)
add Text Listener 
DocumentListener docListener = new DocumentListener() {
    public void insertUpdate(DocumentEvent ev) {
        listener.run();
    public void removeUpdate(DocumentEvent ev) {
        listener.run();
    public void changedUpdate(DocumentEvent ev) {
...
voidaddTextUpdateListener(JTextComponent textComponent, Consumer listener)
add Text Update Listener 
Document doc = textComponent.getDocument();
doc.addDocumentListener(new DocumentListener() {
    @Override
    public void removeUpdate(DocumentEvent e) {
        listener.accept(e);
    @Override
    public void insertUpdate(DocumentEvent e) {
...
voidaddUndoRedo(JTextComponent comp)
add Undo Redo 
final UndoManager undo = new UndoManager();
Document doc = comp.getDocument();
doc.addUndoableEditListener(new UndoableEditListener() {
    public void undoableEditHappened(UndoableEditEvent evt) {
        undo.addEdit(evt.getEdit());
});
ActionMap actionMap = comp.getActionMap();
...
intadjustForLineComment(JTextComponent editor, int iStart)
adjust For Line Comment 
Document doc = editor.getDocument();
Element root = doc.getDefaultRootElement();
Element line = root.getElement(root.getElementIndex(iStart));
int iLineOffset = line.getStartOffset();
int iLength = iStart - iLineOffset;
if (iLength <= 0) {
    return iStart;
String strLine = doc.getText(iLineOffset, iLength);
if (strLine.contains("//")) {
    return iLineOffset;
return iStart;
voidappendToText(JTextComponent textComp, String s)
Appends a String to the end of the document of the JTextComponent 
Document doc = textComp.getDocument();
try {
    doc.insertString(doc.getLength(), s, null);
    textComp.scrollRectToVisible(textComp.modelToView(doc.getLength()));
} catch (BadLocationException e) {
    e.printStackTrace();
voidapplyDefaultProperties(final JTextComponent comp)
Sets default background and foreground color as well as a default font for the specified component. 
if (comp == null) {
    return;
applyProperties(comp, "text", 
        "textText", 
        null);
FontbiggestFont(final javax.swing.text.JTextComponent c)
Gets the biggest font that will fit in the text component. 
Font labelFont = c.getFont();
String labelText = c.getText();
int stringWidth = c.getFontMetrics(labelFont).stringWidth(labelText);
int componentWidth = c.getWidth();
double widthRatio = (double) componentWidth / (double) stringWidth;
int newFontSize = (int) Math.floor(labelFont.getSize() * widthRatio);
int componentHeight = c.getHeight();
int fontSizeToUse = Math.min(newFontSize, componentHeight);
...
voidclear(JTextComponent... fields)
clear 
for (JTextComponent field : fields) {
    field.setText("");